Add search mode option to /api/repo/search (#2756)

* Add repo type option to /api/repo/search

* Add tests and fix result of collaborative filter in specific condition

* Fix/optimize search & tests

* Improve integration tests

* Fix lint errors

* Fix unit tests

* Change and improve internal implementation of repo search

* Use NonexistentID

* Make search api more general

* Change mirror and fork search behaviour

* Fix tests & typo in comment

models/fixtures/access.yml

@@ -62,4 +62,16 @@
   id: 11
   user_id: 18
   repo_id: 21
-  mode: 2 # write
+  mode: 2 # write
+
+-
+  id: 12
+  user_id: 20
+  repo_id: 27
+  mode: 4 # owner
+  
+-
+  id: 13
+  user_id: 20
+  repo_id: 28
+  mode: 4 # owner