small paths code rearrangement (#4007)

small cleanup in paths, primarily splitting files
so that file contents are more clearly owned, which should be a little better for readability and code placement.

Also renames `ServicePrefix` to `BuildPrefix` in
anticipation of multi-service prefixes.

no logic changes, just movement/renaming.

---

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

- [x] ⛔ No

#### Type of change

- [x] 🧹 Tech Debt/Cleanup

#### Issue(s)

* #3993

#### Test Plan

- [x] ⚡ Unit test
- [x] 💚 E2E

src/internal/kopia/base_finder.go

@@ -70,7 +70,7 @@ func (r reason) Category() path.CategoryType {
 }
 
 func (r reason) SubtreePath() (path.Path, error) {
-	p, err := path.ServicePrefix(
+	p, err := path.BuildPrefix(
 		r.Tenant(),
 		r.ProtectedResource(),
 		r.Service(),

src/internal/kopia/upload_test.go

@@ -2865,16 +2865,16 @@ func (suite *HierarchyBuilderUnitSuite) TestBuildDirectoryTreeSelectsMigrateSubt
 		migratedUser = "user_migrate"
 	)
 
-	oldPrefixPathEmail, err := path.ServicePrefix(testTenant, testUser, path.ExchangeService, path.EmailCategory)
+	oldPrefixPathEmail, err := path.BuildPrefix(testTenant, testUser, path.ExchangeService, path.EmailCategory)
 	require.NoError(t, err, clues.ToCore(err))
 
-	newPrefixPathEmail, err := path.ServicePrefix(testTenant, migratedUser, path.ExchangeService, path.EmailCategory)
+	newPrefixPathEmail, err := path.BuildPrefix(testTenant, migratedUser, path.ExchangeService, path.EmailCategory)
 	require.NoError(t, err, clues.ToCore(err))
 
-	oldPrefixPathCont, err := path.ServicePrefix(testTenant, testUser, path.ExchangeService, path.ContactsCategory)
+	oldPrefixPathCont, err := path.BuildPrefix(testTenant, testUser, path.ExchangeService, path.ContactsCategory)
 	require.NoError(t, err, clues.ToCore(err))
 
-	newPrefixPathCont, err := path.ServicePrefix(testTenant, migratedUser, path.ExchangeService, path.ContactsCategory)
+	newPrefixPathCont, err := path.BuildPrefix(testTenant, migratedUser, path.ExchangeService, path.ContactsCategory)
 	require.NoError(t, err, clues.ToCore(err))
 
 	var (

src/internal/m365/graph/collections.go

@@ -79,7 +79,7 @@ func BaseCollections(
 	for cat := range categories {
 		ictx := clues.Add(ctx, "base_service", service, "base_category", cat)
 
-		full, err := path.ServicePrefix(tenant, rOwner, service, cat)
+		full, err := path.BuildPrefix(tenant, rOwner, service, cat)
 		if err != nil {
 			// Shouldn't happen.
 			err = clues.Wrap(err, "making path").WithClues(ictx)

src/internal/m365/graph/collections_test.go

@@ -24,10 +24,10 @@ func (suite *CollectionsUnitSuite) TestNewPrefixCollection() {
 	serv := path.OneDriveService
 	cat := path.FilesCategory
 
-	p1, err := path.ServicePrefix("t", "ro1", serv, cat)
+	p1, err := path.BuildPrefix("t", "ro1", serv, cat)
 	require.NoError(t, err, clues.ToCore(err))
 
-	p2, err := path.ServicePrefix("t", "ro2", serv, cat)
+	p2, err := path.BuildPrefix("t", "ro2", serv, cat)
 	require.NoError(t, err, clues.ToCore(err))
 
 	items, err := path.Build("t", "ro", serv, cat, true, "fld", "itm")

src/internal/m365/service/onedrive/backup.go

@@ -109,7 +109,7 @@ func migrationCollections(
 
 	// unlike exchange, which enumerates all folders on every
 	// backup, onedrive needs to force the owner PN -> ID migration
-	mc, err := path.ServicePrefix(
+	mc, err := path.BuildPrefix(
 		tenant,
 		bpc.ProtectedResource.ID(),
 		path.OneDriveService,
@@ -118,7 +118,7 @@ func migrationCollections(
 		return nil, clues.Wrap(err, "creating user id migration path")
 	}
 
-	mpc, err := path.ServicePrefix(
+	mpc, err := path.BuildPrefix(
 		tenant,
 		bpc.ProtectedResource.Name(),
 		path.OneDriveService,

src/internal/operations/pathtransformer/restore_path_transformer.go

@@ -42,7 +42,7 @@ func locationRef(
 
 func basicLocationPath(repoRef path.Path, locRef *path.Builder) (path.Path, error) {
 	if len(locRef.Elements()) == 0 {
-		res, err := path.ServicePrefix(
+		res, err := path.BuildPrefix(
 			repoRef.Tenant(),
 			repoRef.ResourceOwner(),
 			repoRef.Service(),

src/internal/operations/test/exchange_test.go

@@ -347,7 +347,7 @@ func testExchangeContinuousBackups(suite *ExchangeBackupIntgSuite, toggles contr
 		// },
 	}
 
-	rrPfx, err := path.ServicePrefix(acct.ID(), uidn.ID(), service, path.EmailCategory)
+	rrPfx, err := path.BuildPrefix(acct.ID(), uidn.ID(), service, path.EmailCategory)
 	require.NoError(t, err, clues.ToCore(err))
 
 	// strip the category from the prefix; we primarily want the tenant and resource owner.

src/internal/operations/test/onedrive_test.go

@@ -213,7 +213,7 @@ func runDriveIncrementalTest(
 		}
 	)
 
-	rrPfx, err := path.ServicePrefix(atid, roidn.ID(), service, category)
+	rrPfx, err := path.BuildPrefix(atid, roidn.ID(), service, category)
 	require.NoError(t, err, clues.ToCore(err))
 
 	// strip the category from the prefix; we primarily want the tenant and resource owner.