Timezone feature (#8185)

* Add supported timezones into config

Remove Timezone list creation in favor of timezone from configs

Add Timezone field to Users table

Clean up format of SupportedTimezones in config

* Remove unwanted change

* Add test for updating user timezone

* Add empty map[string]string if Timezone is null

* Add EnableTimezoneSelection config

* Revert back to map[string]string for ClientConfig

* Refactor SupportedTimezones into timezones.json

* Include timezones.json in TestConfigFlag

* Add timezone api endpoint

* Bump varchar size to 256 and setMaxSize in user_store

* Refactor LoadConfig to LoadConfig and LoadTimezoneConfig

* Remove unnecessary argument in LoadConfig, mail_test

* Add test for timezone endpoint

* Add license header

* Refactor timezones endpoint to system.go

* Add system base route to timezone endpoint

* db timezone upgrade in db v4.9

* Avoid saving SupportedTimezones to config.json

* Add timezonePath support in config

* Remove EnableTimezoneSelection from config

* Use return statement without return parameter

* Refactor test for SupportedTimezones

* Check for supportedTimezone != nil instead of using len

* Decouple SupportedTimezones out of Config

* Fix failing test

* Add LastTeamIconUpdate back in upgrade.go

* Write timezone config in config_flag_test

* Add code fallback for default timezone support

api4/system_test.go

@@ -527,3 +527,15 @@ func TestS3TestConnection(t *testing.T) {
 		t.Fatal("should return error ")
 	}
 }
+
+func TestSupportedTimezones(t *testing.T) {
+	th := Setup().InitBasic()
+	defer th.TearDown()
+	Client := th.Client
+
+	supportedTimezonesFromConfig := th.App.Timezones()
+	supportedTimezones, resp := Client.GetSupportedTimezone()
+
+	CheckNoError(t, resp)
+	assert.Equal(t, supportedTimezonesFromConfig, supportedTimezones)
+}