Minor refactoring of graph error checking code (#3686)

Minor code cleanup to error checking and calling code:
- Remove unused function
- Update error check for folder not found
- Remove duplicate check in SDK function

---

#### 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

- [ ] 🌻 Feature
- [ ] 🐛 Bugfix
- [ ] 🗺️ Documentation
- [ ] 🤖 Supportability/Tests
- [ ] 💻 CI/Deployment
- [x] 🧹 Tech Debt/Cleanup

#### Issue(s)

* fixes #3684

#### Test Plan

- [ ] 💪 Manual
- [x] ⚡ Unit test
- [ ] 💚 E2E

src/internal/m365/graph/errors.go

@@ -131,7 +131,9 @@ func IsErrQuotaExceeded(err error) bool {
 }
 
 func IsErrExchangeMailFolderNotFound(err error) bool {
-	return hasErrorCode(err, ResourceNotFound, MailboxNotEnabledForRESTAPI)
+	// Not sure if we can actually see a resourceNotFound error here. I've only
+	// seen the latter two.
+	return hasErrorCode(err, ResourceNotFound, itemNotFound, MailboxNotEnabledForRESTAPI)
 }
 
 func IsErrUserNotFound(err error) bool {
@@ -153,10 +155,6 @@ func IsErrUserNotFound(err error) bool {
 	return false
 }
 
-func IsErrResourceNotFound(err error) bool {
-	return hasErrorCode(err, ResourceNotFound)
-}
-
 func IsErrCannotOpenFileAttachment(err error) bool {
 	return hasErrorCode(err, cannotOpenFileAttachment)
 }

src/internal/m365/graph/errors_test.go

@@ -255,13 +255,27 @@ func (suite *GraphErrorsUnitSuite) TestIsErrUserNotFound() {
 		{
 			name: "resource not found oDataErr",
 			err: func() error {
-				res := odErr(string(ResourceNotFound))
-				res.GetError().SetMessage(ptr.To("User not found"))
-
+				res := odErrMsg(string(ResourceNotFound), "User not found")
 				return res
 			}(),
 			expect: assert.True,
 		},
+		{
+			name: "resource not found oDataErr wrapped",
+			err: func() error {
+				res := odErrMsg(string(ResourceNotFound), "User not found")
+				return clues.Wrap(res, "getting mail folder")
+			}(),
+			expect: assert.True,
+		},
+		{
+			name: "resource not found oDataErr stacked",
+			err: func() error {
+				res := odErrMsg(string(ResourceNotFound), "User not found")
+				return clues.Stack(res, assert.AnError)
+			}(),
+			expect: assert.True,
+		},
 	}
 	for _, test := range table {
 		suite.Run(test.name, func() {

src/pkg/services/m365/m365.go

@@ -90,10 +90,6 @@ func UserHasMailbox(ctx context.Context, acct account.Account, userID string) (b
 			return false, clues.Stack(graph.ErrResourceOwnerNotFound, err)
 		}
 
-		if graph.IsErrExchangeMailFolderNotFound(err) {
-			return false, nil
-		}
-
 		return false, clues.Stack(err)
 	}