MM-19250 - new endpoint to retrieve command by id (#13598)

* MM-19250 add endpoint to retrieve command by id

* endpoint
* client
* unit tests

* MM-19250 update comment; remove redundant unit test

* MM-19250 rename GetCommand to GetCommandById

* MM-19250 don't filter on autocomplete flag

* MM-19250: require team_id when using GetCommandById

* team_id added to endpoint query string for GET
* unit test to check for mismatch teamid param and command teamid

* Revert "MM-19250: require team_id when using GetCommandById"

This reverts commit ed78e2796426f75bc23d0f16064be95fa37305fd.

* MM-19250 don't leak existence of id when user doesn't have perms

* return 404 not_found when id not found
* return 404 not_found when id exists but user missing perms to view team
* return 404 not_found when id exists but user missing perms to manage commands

* MM-19250 fix typos in comments

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

web/context.go

@@ -169,6 +169,10 @@ func (c *Context) SetServerBusyError() {
 	c.Err = NewServerBusyError()
 }
 
+func (c *Context) SetCommandNotFoundError() {
+	c.Err = model.NewAppError("GetCommand", "store.sql_command.save.get.app_error", nil, "", http.StatusNotFound)
+}
+
 func (c *Context) HandleEtag(etag string, routeName string, w http.ResponseWriter, r *http.Request) bool {
 	metrics := c.App.Metrics
 	if et := r.Header.Get(model.HEADER_ETAG_CLIENT); len(etag) > 0 {