PLT-4938 Add app package and move logic over from api package (#4931)

* Add app package and move logic over from api package

* Change app package functions to return errors

* Move non-api tests into app package

* Fix merge

api/api.go

@@ -7,6 +7,7 @@ import (
 	"net/http"
 
 	"github.com/gorilla/mux"
+	"github.com/mattermost/platform/app"
 	"github.com/mattermost/platform/einterfaces"
 	"github.com/mattermost/platform/model"
 	"github.com/mattermost/platform/utils"
@@ -53,16 +54,20 @@ type Routes struct {
 	Emoji *mux.Router // 'api/v3/emoji'
 
 	Webrtc *mux.Router // 'api/v3/webrtc'
-
-	WebSocket *WebSocketRouter // websocket api
 }
 
 var BaseRoutes *Routes
 
+func InitRouter() {
+	app.Srv.Router = mux.NewRouter()
+	app.Srv.Router.NotFoundHandler = http.HandlerFunc(Handle404)
+	app.Srv.WebSocketRouter = app.NewWebSocketRouter()
+}
+
 func InitApi() {
 	BaseRoutes = &Routes{}
-	BaseRoutes.Root = Srv.Router
-	BaseRoutes.ApiRoot = Srv.Router.PathPrefix(model.API_URL_SUFFIX).Subrouter()
+	BaseRoutes.Root = app.Srv.Router
+	BaseRoutes.ApiRoot = app.Srv.Router.PathPrefix(model.API_URL_SUFFIX).Subrouter()
 	BaseRoutes.Users = BaseRoutes.ApiRoot.PathPrefix("/users").Subrouter()
 	BaseRoutes.NeedUser = BaseRoutes.Users.PathPrefix("/{user_id:[A-Za-z0-9]+}").Subrouter()
 	BaseRoutes.Teams = BaseRoutes.ApiRoot.PathPrefix("/teams").Subrouter()
@@ -86,8 +91,6 @@ func InitApi() {
 	BaseRoutes.Emoji = BaseRoutes.ApiRoot.PathPrefix("/emoji").Subrouter()
 	BaseRoutes.Webrtc = BaseRoutes.ApiRoot.PathPrefix("/webrtc").Subrouter()
 
-	BaseRoutes.WebSocket = NewWebSocketRouter()
-
 	InitUser()
 	InitTeam()
 	InitChannel()
@@ -108,11 +111,11 @@ func InitApi() {
 	InitDeprecated()
 
 	// 404 on any api route before web.go has a chance to serve it
-	Srv.Router.Handle("/api/{anything:.*}", http.HandlerFunc(Handle404))
+	app.Srv.Router.Handle("/api/{anything:.*}", http.HandlerFunc(Handle404))
 
 	utils.InitHTML()
 
-	InitEmailBatching()
+	app.InitEmailBatching()
 }
 
 func HandleEtag(etag string, routeName string, w http.ResponseWriter, r *http.Request) bool {