handles single & multiple values for metadata columns (#5121)

handles single & multiple values for metadata columns

Similar to `Hyperlink` and `Column` columns, `Metadata` column too is unrecognizable from GRAPH API response. Hence identifying from the field column names.

`Metadata` fields are like tags. A `Metadata` fields can be configured to hold multiple values/tags

**Original List with `Metadata` column (Department) with single value/tag**:
![Metadata-List](https://github.com/alcionai/corso/assets/48874082/0b913a2a-46d5-4d9c-83f9-69a5236b1024)

**Restored List with `Metadata` column with single value/tag**:
![Restored-Metadata-List](https://github.com/alcionai/corso/assets/48874082/9420012b-345c-4fac-90c3-c0d421b2edfb)

**Original List with `Metadata` column (Department) with multiple value/tag**:
![Metadata-List-Multi](https://github.com/alcionai/corso/assets/48874082/054ef4a1-c46e-48ba-b410-a95b540cde33)

**Restored List with `Metadata` column with multiple value/tag**:
![Restored-Multi-Metadata-List](https://github.com/alcionai/corso/assets/48874082/ef6c904b-e431-4a85-9ef2-f08bcf8e21e4)


#### Does this PR need a docs update or release note?

- [ ] ✅ Yes, it's included
- [ ] 🕐 Yes, but in a later PR
- [x] ⛔ No

#### Type of change

<!--- Please check the type of change your PR introduces: --->
- [x] 🌻 Feature
- [ ] 🐛 Bugfix
- [ ] 🗺️ Documentation
- [ ] 🤖 Supportability/Tests
- [ ] 💻 CI/Deployment
- [ ] 🧹 Tech Debt/Cleanup

#### Issue(s)
#5084 
#5108 

#### Test Plan

<!-- How will this be tested prior to merging.-->
- [x] 💪 Manual
- [x] ⚡ Unit test
- [x] 💚 E2E

src/pkg/services/m365/api/consts.go

@@ -62,6 +62,10 @@ const (
 
 	PersonEmailKey = "Email"
 
+	MetadataLabelKey    = "Label"
+	MetadataTermGUIDKey = "TermGuid"
+	MetadataWssIDKey    = "WssId"
+
 	LinkTitleFieldNamePart  = "LinkTitle"
 	ChildCountFieldNamePart = "ChildCount"
 	LookupIDFieldNamePart   = "LookupId"

src/pkg/services/m365/api/lists.go

@@ -511,6 +511,10 @@ func retrieveFieldData(orig models.FieldValueSetable, columnNames map[string]*co
 		additionalData[fieldName] = concatenatedHyperlink
 	}
 
+	if metadataField, fieldName, ok := hasMetadataFields(additionalData); ok {
+		additionalData[fieldName] = concatenateMetadataFields(metadataField)
+	}
+
 	fields.SetAdditionalData(additionalData)
 
 	return fields
@@ -647,6 +651,44 @@ func hasHyperLinkFields(additionalData map[string]any) (map[string]any, string,
 	return nil, "", false
 }
 
+func hasMetadataFields(additionalData map[string]any) ([]map[string]any, string, bool) {
+	for fieldName, value := range additionalData {
+		switch valType := reflect.TypeOf(value).Kind(); valType {
+		case reflect.Map:
+			metadataFields, areMetadataFields := getMetadataFields(value)
+			if areMetadataFields {
+				return []map[string]any{metadataFields}, fieldName, true
+			}
+
+		case reflect.Slice:
+			mmdfs := make([]map[string]any, 0)
+
+			multiMetadataFields, ok := value.([]any)
+			if !ok {
+				continue
+			}
+
+			for _, mdfs := range multiMetadataFields {
+				metadataFields, areMetadataFields := getMetadataFields(mdfs)
+				if areMetadataFields {
+					mmdfs = append(mmdfs, metadataFields)
+				}
+			}
+
+			if len(mmdfs) > 0 {
+				return mmdfs, fieldName, true
+			}
+		}
+	}
+
+	return nil, "", false
+}
+
+func getMetadataFields(metadataFieldvalue any) (map[string]any, bool) {
+	nestedFields, ok := metadataFieldvalue.(map[string]any)
+	return nestedFields, ok && keys.HasKeys(nestedFields, MetadataLabelKey, MetadataTermGUIDKey, MetadataWssIDKey)
+}
+
 func concatenateAddressFields(addressFields map[string]any) string {
 	parts := make([]string, 0)
 
@@ -692,6 +734,23 @@ func concatenateHyperLinkFields(hyperlinkFields map[string]any) string {
 	return ""
 }
 
+func concatenateMetadataFields(metadataFieldsArr []map[string]any) string {
+	labels := make([]string, 0)
+
+	for _, md := range metadataFieldsArr {
+		mdVal, ok := md[MetadataLabelKey].(*string)
+		if ok {
+			labels = append(labels, ptr.Val(mdVal))
+		}
+	}
+
+	if len(labels) > 0 {
+		return strings.Join(labels, ",")
+	}
+
+	return ""
+}
+
 func addressKeyToVal(fields map[string]any, key string) string {
 	if v, err := str.AnyValueToString(key, fields); err == nil {
 		return v

src/pkg/services/m365/api/lists_test.go

@@ -941,6 +941,161 @@ func (suite *ListsUnitSuite) TestSetAdditionalDataByColumnNames() {
 	}
 }
 
+func (suite *ListsUnitSuite) TestHasMetadataFields() {
+	t := suite.T()
+
+	tests := []struct {
+		name              string
+		additionalData    map[string]any
+		expectedFields    []map[string]any
+		expectedFieldName string
+		hasMetadataFields bool
+	}{
+		{
+			name: "Single metadata fields, has all keys",
+			additionalData: map[string]any{
+				"MdCol": map[string]any{
+					MetadataLabelKey:    ptr.To("Engineering"),
+					MetadataTermGUIDKey: ptr.To("6b5d3ce9-3043-499f-8be6-e92fb57bed96"),
+					MetadataWssIDKey:    ptr.To(4),
+				},
+			},
+			expectedFields: []map[string]any{
+				{
+					MetadataLabelKey:    ptr.To("Engineering"),
+					MetadataTermGUIDKey: ptr.To("6b5d3ce9-3043-499f-8be6-e92fb57bed96"),
+					MetadataWssIDKey:    ptr.To(4),
+				},
+			},
+			expectedFieldName: "MdCol",
+			hasMetadataFields: true,
+		},
+		{
+			name: "Multiple metadata fields, has all keys",
+			additionalData: map[string]any{
+				"MdCol": []any{
+					map[string]any{
+						MetadataLabelKey:    ptr.To("Engineering"),
+						MetadataTermGUIDKey: ptr.To("6b5d3ce9-3043-499f-8be6-e92fb57bed96"),
+						MetadataWssIDKey:    ptr.To(4),
+					},
+					map[string]any{
+						MetadataLabelKey:    ptr.To("Marketing"),
+						MetadataTermGUIDKey: ptr.To("312347ce-3043-499f-8be6-e92fb57bed96"),
+						MetadataWssIDKey:    ptr.To(2),
+					},
+				},
+			},
+			expectedFields: []map[string]any{
+				{
+					MetadataLabelKey:    ptr.To("Engineering"),
+					MetadataTermGUIDKey: ptr.To("6b5d3ce9-3043-499f-8be6-e92fb57bed96"),
+					MetadataWssIDKey:    ptr.To(4),
+				},
+				{
+					MetadataLabelKey:    ptr.To("Marketing"),
+					MetadataTermGUIDKey: ptr.To("312347ce-3043-499f-8be6-e92fb57bed96"),
+					MetadataWssIDKey:    ptr.To(2),
+				},
+			},
+			expectedFieldName: "MdCol",
+			hasMetadataFields: true,
+		},
+		{
+			name: "Single metadata fields, missing few keys",
+			additionalData: map[string]any{
+				"MdCol": map[string]any{
+					MetadataLabelKey: ptr.To("Engineering"),
+				},
+			},
+			expectedFields:    nil,
+			expectedFieldName: "",
+			hasMetadataFields: false,
+		},
+		{
+			name: "Multiple metadata fields, missing few keys",
+			additionalData: map[string]any{
+				"MdCol": []any{
+					map[string]any{
+						MetadataLabelKey:    ptr.To("Engineering"),
+						MetadataTermGUIDKey: ptr.To("6b5d3ce9-3043-499f-8be6-e92fb57bed96"),
+						MetadataWssIDKey:    ptr.To(4),
+					},
+					map[string]any{
+						MetadataLabelKey: ptr.To("Marketing"),
+					},
+				},
+			},
+			expectedFields: []map[string]any{
+				{
+					MetadataLabelKey:    ptr.To("Engineering"),
+					MetadataTermGUIDKey: ptr.To("6b5d3ce9-3043-499f-8be6-e92fb57bed96"),
+					MetadataWssIDKey:    ptr.To(4),
+				},
+			},
+			expectedFieldName: "MdCol",
+			hasMetadataFields: true,
+		},
+	}
+
+	for _, test := range tests {
+		suite.Run(test.name, func() {
+			nestedFields, fName, isMetadata := hasMetadataFields(test.additionalData)
+			assert.Equal(t, test.expectedFields, nestedFields)
+			assert.Equal(t, test.expectedFieldName, fName)
+			assert.Equal(t, test.hasMetadataFields, isMetadata)
+		})
+	}
+}
+
+func (suite *ListsUnitSuite) TestConcatenateMetadataFields() {
+	t := suite.T()
+
+	tests := []struct {
+		name              string
+		metadataFields    []map[string]any
+		expectedFieldName string
+		expectedResult    string
+		hasMetadataFields bool
+		columnNames       map[string]any
+	}{
+		{
+			name: "Single metadata fields",
+			metadataFields: []map[string]any{
+				{
+					MetadataLabelKey:    ptr.To("Engineering"),
+					MetadataTermGUIDKey: ptr.To("6b5d3ce9-3043-499f-8be6-e92fb57bed96"),
+					MetadataWssIDKey:    ptr.To(4),
+				},
+			},
+			expectedResult: "Engineering",
+		},
+		{
+			name: "Multiple metadata fields",
+			metadataFields: []map[string]any{
+				{
+					MetadataLabelKey:    ptr.To("Engineering"),
+					MetadataTermGUIDKey: ptr.To("6b5d3ce9-3043-499f-8be6-e92fb57bed96"),
+					MetadataWssIDKey:    ptr.To(4),
+				},
+				{
+					MetadataLabelKey:    ptr.To("Marketing"),
+					MetadataTermGUIDKey: ptr.To("312347ce-3043-499f-8be6-e92fb57bed96"),
+					MetadataWssIDKey:    ptr.To(2),
+				},
+			},
+			expectedResult: "Engineering,Marketing",
+		},
+	}
+
+	for _, test := range tests {
+		suite.Run(test.name, func() {
+			res := concatenateMetadataFields(test.metadataFields)
+			assert.Equal(t, test.expectedResult, res)
+		})
+	}
+}
+
 func (suite *ListsUnitSuite) TestCheckFields() {
 	t := suite.T()