Return interface values instead of concrete type (#1696)

## Description

Having a map of interface values instead of concrete structs allows adding collection implementations via different structs. This will be useful to inject a new collection that contains metadata information like delta links.

Also refactors the code for creating collections in Exchange so that it follows golang patterns of exiting early a bit better.

## Type of change

<!--- Please check the type of change your PR introduces: --->
- [ ] 🌻 Feature
- [ ] 🐛 Bugfix
- [ ] 🗺️ Documentation
- [ ] 🤖 Test
- [ ] 💻 CI/Deployment
- [x] 🐹 Trivial/Minor

## Issue(s)

* #1685

## Test Plan

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

src/internal/connector/data_collections.go

@@ -109,16 +109,16 @@ func verifyBackupInputs(sels selectors.Selector, userPNs, siteIDs []string) erro
 func (gc *GraphConnector) createExchangeCollections(
 	ctx context.Context,
 	scope selectors.ExchangeScope,
-) ([]*exchange.Collection, error) {
+) ([]data.Collection, error) {
 	var (
 		errs           *multierror.Error
 		users          = scope.Get(selectors.ExchangeUser)
-		allCollections = make([]*exchange.Collection, 0)
+		allCollections = make([]data.Collection, 0)
 	)
 
 	// Create collection of ExchangeDataCollection
 	for _, user := range users {
-		collections := make(map[string]*exchange.Collection)
+		collections := make(map[string]data.Collection)
 
 		qp := graph.QueryParams{
 			Category:      scope.Category().PathType(),
@@ -188,9 +188,7 @@ func (gc *GraphConnector) ExchangeDataCollection(
 			return nil, support.WrapAndAppend(user[0], err, errs)
 		}
 
-		for _, collection := range dcs {
-			collections = append(collections, collection)
-		}
+		collections = append(collections, dcs...)
 	}
 
 	return collections, errs

src/internal/connector/data_collections_test.go

@@ -11,6 +11,7 @@ import (
 	"github.com/alcionai/corso/src/internal/connector/exchange"
 	"github.com/alcionai/corso/src/internal/connector/sharepoint"
 	"github.com/alcionai/corso/src/internal/connector/support"
+	"github.com/alcionai/corso/src/internal/data"
 	"github.com/alcionai/corso/src/internal/tester"
 	"github.com/alcionai/corso/src/pkg/selectors"
 )
@@ -336,11 +337,11 @@ func (suite *ConnectorCreateExchangeCollectionIntegrationSuite) TestContactSeria
 
 	tests := []struct {
 		name          string
-		getCollection func(t *testing.T) []*exchange.Collection
+		getCollection func(t *testing.T) []data.Collection
 	}{
 		{
 			name: "Default Contact Folder",
-			getCollection: func(t *testing.T) []*exchange.Collection {
+			getCollection: func(t *testing.T) []data.Collection {
 				scope := selectors.
 					NewExchangeBackup().
 					ContactFolders([]string{suite.user}, []string{exchange.DefaultContactFolder}, selectors.PrefixMatch())[0]
@@ -389,12 +390,12 @@ func (suite *ConnectorCreateExchangeCollectionIntegrationSuite) TestEventsSerial
 
 	tests := []struct {
 		name, expected string
-		getCollection  func(t *testing.T) []*exchange.Collection
+		getCollection  func(t *testing.T) []data.Collection
 	}{
 		{
 			name:     "Default Event Calendar",
 			expected: exchange.DefaultCalendar,
-			getCollection: func(t *testing.T) []*exchange.Collection {
+			getCollection: func(t *testing.T) []data.Collection {
 				sel := selectors.NewExchangeBackup()
 				sel.Include(sel.EventCalendars([]string{suite.user}, []string{exchange.DefaultCalendar}, selectors.PrefixMatch()))
 				collections, err := connector.createExchangeCollections(ctx, sel.Scopes()[0])
@@ -406,7 +407,7 @@ func (suite *ConnectorCreateExchangeCollectionIntegrationSuite) TestEventsSerial
 		{
 			name:     "Birthday Calendar",
 			expected: "Birthdays",
-			getCollection: func(t *testing.T) []*exchange.Collection {
+			getCollection: func(t *testing.T) []data.Collection {
 				sel := selectors.NewExchangeBackup()
 				sel.Include(sel.EventCalendars([]string{suite.user}, []string{"Birthdays"}, selectors.PrefixMatch()))
 				collections, err := connector.createExchangeCollections(ctx, sel.Scopes()[0])

src/internal/connector/exchange/service_iterators.go

@@ -14,6 +14,7 @@ import (
 
 	"github.com/alcionai/corso/src/internal/connector/graph"
 	"github.com/alcionai/corso/src/internal/connector/support"
+	"github.com/alcionai/corso/src/internal/data"
 	"github.com/alcionai/corso/src/pkg/path"
 	"github.com/alcionai/corso/src/pkg/selectors"
 )
@@ -24,9 +25,9 @@ const nextLinkKey = "@odata.nextLink"
 // the value is not in the map returns an empty string.
 func getAdditionalDataString(
 	key string,
-	data map[string]any,
+	addtlData map[string]any,
 ) string {
-	iface := data[key]
+	iface := addtlData[key]
 	if iface == nil {
 		return ""
 	}
@@ -47,45 +48,45 @@ func getAdditionalDataString(
 func FilterContainersAndFillCollections(
 	ctx context.Context,
 	qp graph.QueryParams,
-	collections map[string]*Collection,
+	collections map[string]data.Collection,
 	statusUpdater support.StatusUpdater,
 	resolver graph.ContainerResolver,
 	scope selectors.ExchangeScope,
 ) error {
 	var (
-		collectionType = CategoryToOptionIdentifier(scope.Category().PathType())
 		errs           error
+		collectionType = CategoryToOptionIdentifier(qp.Category)
 	)
 
 	for _, c := range resolver.Items() {
 		dirPath, ok := pathAndMatch(qp, c, scope)
-		if ok {
-			// Create only those that match
-			service, err := createService(qp.Credentials, qp.FailFast)
-			if err != nil {
-				errs = support.WrapAndAppend(
-					qp.ResourceOwner+" FilterContainerAndFillCollection",
-					err,
-					errs)
-
-				if qp.FailFast {
-					return errs
-				}
-			}
-
-			edc := NewCollection(
-				qp.ResourceOwner,
-				dirPath,
-				collectionType,
-				service,
-				statusUpdater,
-			)
-			collections[*c.GetId()] = &edc
+		if !ok {
+			continue
 		}
-	}
 
-	for directoryID, col := range collections {
-		fetchFunc, err := getFetchIDFunc(scope.Category().PathType())
+		// Create only those that match
+		service, err := createService(qp.Credentials, qp.FailFast)
+		if err != nil {
+			errs = support.WrapAndAppend(
+				qp.ResourceOwner+" FilterContainerAndFillCollection",
+				err,
+				errs)
+
+			if qp.FailFast {
+				return errs
+			}
+		}
+
+		edc := NewCollection(
+			qp.ResourceOwner,
+			dirPath,
+			collectionType,
+			service,
+			statusUpdater,
+		)
+		collections[*c.GetId()] = &edc
+
+		fetchFunc, err := getFetchIDFunc(qp.Category)
 		if err != nil {
 			errs = support.WrapAndAppend(
 				qp.ResourceOwner,
@@ -99,7 +100,7 @@ func FilterContainersAndFillCollections(
 			continue
 		}
 
-		jobs, err := fetchFunc(ctx, col.service, qp.ResourceOwner, directoryID)
+		jobs, err := fetchFunc(ctx, edc.service, qp.ResourceOwner, *c.GetId())
 		if err != nil {
 			errs = support.WrapAndAppend(
 				qp.ResourceOwner,
@@ -108,7 +109,7 @@ func FilterContainersAndFillCollections(
 			)
 		}
 
-		col.jobs = append(col.jobs, jobs...)
+		edc.jobs = append(edc.jobs, jobs...)
 	}
 
 	return errs