[API] Migration: Change ServiceType String (#12672)

* use different structs for MigrateRepoOptions on UI and API

* Fix TokenAuth and rename UID to an understandable Name

* fix swagger doc

* simplify & mk redable

* R E F A C T O R:
migration has now internal 3 structs to store its options:
 * the Options for WebUI: modules/auth/repo_form.go
 * the Options for API: modules/structs/repo.go
 * the option struct with after validation for internal prossessing: modules/migrations/base/options.go

* Copyright Header

* Deprecate UID - add RepoOwner

* adopt repo.go -> migrate.go

* add comment about each struct purpose

* lint

modules/migrations/gitea_test.go

@@ -12,6 +12,7 @@ import (
 
 	"code.gitea.io/gitea/models"
 	"code.gitea.io/gitea/modules/graceful"
+	"code.gitea.io/gitea/modules/migrations/base"
 	"code.gitea.io/gitea/modules/structs"
 	"code.gitea.io/gitea/modules/util"
 
@@ -32,7 +33,7 @@ func TestGiteaUploadRepo(t *testing.T) {
 		uploader   = NewGiteaLocalUploader(graceful.GetManager().HammerContext(), user, user.Name, repoName)
 	)
 
-	err := migrateRepository(downloader, uploader, structs.MigrateRepoOption{
+	err := migrateRepository(downloader, uploader, base.MigrateOptions{
 		CloneAddr:    "https://github.com/go-xorm/builder",
 		RepoName:     repoName,
 		AuthUsername: "",