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>

model/client4.go

@@ -4015,6 +4015,17 @@ func (c *Client4) ListCommands(teamId string, customOnly bool) ([]*Command, *Res
 	return CommandListFromJson(r.Body), BuildResponse(r)
 }
 
+// GetCommandById will retrieve a command by id.
+func (c *Client4) GetCommandById(cmdId string) (*Command, *Response) {
+	url := fmt.Sprintf("%s/%s", c.GetCommandsRoute(), cmdId)
+	r, err := c.DoApiGet(url, "")
+	if err != nil {
+		return nil, BuildErrorResponse(r, err)
+	}
+	defer closeBody(r)
+	return CommandFromJson(r.Body), BuildResponse(r)
+}
+
 // ExecuteCommand executes a given slash command.
 func (c *Client4) ExecuteCommand(channelId, command string) (*CommandResponse, *Response) {
 	commandArgs := &CommandArgs{