MM-10140: API Implementation for Schemes related Endpoints (#8615)

* Implement basic scheme CRUD endpoints.

* Get All Schemes (Paged) Endpoint and store plumbing.

* Add get teams/channels for schemes.

* Fix unit tests.

* Review fixes.

* More review fixes.

api4/api.go

@@ -99,7 +99,8 @@ type Routes struct {
 
 	Reactions *mux.Router // 'api/v4/reactions'
 
-	Roles *mux.Router // 'api/v4/roles'
+	Roles   *mux.Router // 'api/v4/roles'
+	Schemes *mux.Router // 'api/v4/schemes'
 
 	Emojis      *mux.Router // 'api/v4/emoji'
 	Emoji       *mux.Router // 'api/v4/emoji/{emoji_id:[A-Za-z0-9]+}'
@@ -200,6 +201,7 @@ func Init(a *app.App, root *mux.Router, full bool) *API {
 	api.BaseRoutes.OpenGraph = api.BaseRoutes.ApiRoot.PathPrefix("/opengraph").Subrouter()
 
 	api.BaseRoutes.Roles = api.BaseRoutes.ApiRoot.PathPrefix("/roles").Subrouter()
+	api.BaseRoutes.Schemes = api.BaseRoutes.ApiRoot.PathPrefix("/schemes").Subrouter()
 
 	api.BaseRoutes.Image = api.BaseRoutes.ApiRoot.PathPrefix("/image").Subrouter()
 
@@ -229,6 +231,7 @@ func Init(a *app.App, root *mux.Router, full bool) *API {
 	api.InitOpenGraph()
 	api.InitPlugin()
 	api.InitRole()
+	api.InitScheme()
 	api.InitImage()
 
 	root.Handle("/api/v4/{anything:.*}", http.HandlerFunc(Handle404))