Convert bool string comparisons to strconv.ParseBool for REST parameters (#13650)

* Convert bool string comparisons to strconv.ParseBool for REST parameters

* Log failed bool conversions

* Rename errors, changed log levels

* drop strconv.ParseBool error handling

If the query string parameter is omitted, strconv.ParseBool returns an error for the empty strings, which spams the logs. Instead, just assume the default semantics of a `false` return value if an error occurs.

* allow randomized Client4 booleans

It's hard to test api4's handling of the various boolean input values
accepted. Extend Client4 with support for overriding how it builds those
strings, and pick a random value on test startup.

* gofmt -s

Co-authored-by: mattermod <mattermod@users.noreply.github.com>
Co-authored-by: Ben Schumacher <ben.schumacher@mattermost.com>
Co-authored-by: Jesse Hallam <jesse.hallam@gmail.com>

api4/command.go

@@ -213,10 +213,7 @@ func deleteCommand(c *Context, w http.ResponseWriter, r *http.Request) {
 }
 
 func listCommands(c *Context, w http.ResponseWriter, r *http.Request) {
-	customOnly, failConv := strconv.ParseBool(r.URL.Query().Get("custom_only"))
-	if failConv != nil {
-		customOnly = false
-	}
+	customOnly, _ := strconv.ParseBool(r.URL.Query().Get("custom_only"))
 
 	teamId := r.URL.Query().Get("team_id")
 	if len(teamId) == 0 {