MM-32396 Create endpoint for listing all the roles (#16988)

* Create an endpoint for listing roles

* Add function to client model

* Create tests for listing roles endpoint

* Apply code review suggestions

* Restore GetAllRoles app method

* Use AppContext instead of App

* Minor fix

* Refactor according to new changes

Co-authored-by: Mattermod <mattermod@users.noreply.github.com>

api4/role.go

@@ -19,12 +19,34 @@ var notAllowedPermissions = []string{
 }
 
 func (api *API) InitRole() {
+	api.BaseRoutes.Roles.Handle("", api.APISessionRequired(getAllRoles)).Methods("GET")
 	api.BaseRoutes.Roles.Handle("/{role_id:[A-Za-z0-9]+}", api.APISessionRequiredTrustRequester(getRole)).Methods("GET")
 	api.BaseRoutes.Roles.Handle("/name/{role_name:[a-z0-9_]+}", api.APISessionRequiredTrustRequester(getRoleByName)).Methods("GET")
 	api.BaseRoutes.Roles.Handle("/names", api.APISessionRequiredTrustRequester(getRolesByNames)).Methods("POST")
 	api.BaseRoutes.Roles.Handle("/{role_id:[A-Za-z0-9]+}/patch", api.APISessionRequired(patchRole)).Methods("PUT")
 }
 
+func getAllRoles(c *Context, w http.ResponseWriter, r *http.Request) {
+	if !c.App.SessionHasPermissionTo(*c.AppContext.Session(), model.PermissionManageSystem) {
+		c.SetPermissionError(model.PermissionManageSystem)
+		return
+	}
+
+	roles, err := c.App.GetAllRoles()
+	if err != nil {
+		c.Err = err
+		return
+	}
+
+	js, jsonErr := json.Marshal(roles)
+	if jsonErr != nil {
+		c.Err = model.NewAppError("getAllRoles", "api.marshal_error", nil, jsonErr.Error(), http.StatusInternalServerError)
+		return
+	}
+
+	w.Write(js)
+}
+
 func getRole(c *Context, w http.ResponseWriter, r *http.Request) {
 	c.RequireRoleId()
 	if c.Err != nil {