[MM-20684] Slash Command Autocomplete (#14557)

* [MM-20684] Initial implementation of the Command Autocomplete (#13602)

* Implement Autocomplete Data

* Change CommandName to Trigger

* Fix Autocomplete test

* Make stylistic changes

* Rename a bunch of fields and methods

* Fix variable names, safer type assertions

* [MM-20684] plugin autocomplete implementation (#14259)

* Add an endpoint for command autocomplete suggestions

* Add full Suggestion to the AutocompleteSugestion struct

* Add Dynamic Argument support

* Tidy up things

* Fix missed test case

* Add support of the named arguments

* Update autocomplete API

Fix review issues

Implement dynamic args as a local request

* Fix ineffassign

* Add support of the uppercase letters in arguments

* Add support of the optional arguments

* Remove ineffectual assignment

* Add support for icons (#14489)

* Address couple of nits

* Add comment to IconData

* Add types to all consts

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

model/client4.go

@@ -4157,6 +4157,17 @@ func (c *Client4) ListCommands(teamId string, customOnly bool) ([]*Command, *Res
 	return CommandListFromJson(r.Body), BuildResponse(r)
 }
 
+// ListCommandAutocompleteSuggestions will retrieve a list of suggestions for a userInput.
+func (c *Client4) ListCommandAutocompleteSuggestions(userInput, teamId string) ([]AutocompleteSuggestion, *Response) {
+	query := fmt.Sprintf("/commands/autocomplete_suggestions?user_input=%v", userInput)
+	r, err := c.DoApiGet(c.GetTeamRoute(teamId)+query, "")
+	if err != nil {
+		return nil, BuildErrorResponse(r, err)
+	}
+	defer closeBody(r)
+	return AutocompleteSuggestionsFromJSON(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)