Provisioning: Allows specifying uid for datasource and use that in derived fields (#23585)

* Add uid to datasource

* Fix uid passing when provisioning

* Better error handling and Uid column type change

* Fix test and strict null error counts

* Add backend tests

* Add tests

* Fix strict null checks

* Update test

* Improve tests

* Update pkg/services/sqlstore/datasource.go

Co-Authored-By: Arve Knudsen <arve.knudsen@gmail.com>

* Variable rename

Co-authored-by: Arve Knudsen <arve.knudsen@gmail.com>

pkg/services/sqlstore/migrator/mysql_dialect.go

@@ -148,6 +148,13 @@ func (db *Mysql) IsUniqueConstraintViolation(err error) bool {
 	return db.isThisError(err, mysqlerr.ER_DUP_ENTRY)
 }
 
+func (db *Mysql) ErrorMessage(err error) string {
+	if driverErr, ok := err.(*mysql.MySQLError); ok {
+		return driverErr.Message
+	}
+	return ""
+}
+
 func (db *Mysql) IsDeadlock(err error) bool {
 	return db.isThisError(err, mysqlerr.ER_LOCK_DEADLOCK)
 }