Admin authentication required fields not respected

[willemvd]

• Gitea version (or commit ref): 1.0.0
• Can you reproduce the bug at https://try.gitea.io:
  Not possible, admins only

Description

On the admin/auths/new page the required fields are not respected, only exception are the 'Authentication Type' and 'Authentication Name' fields.
Other required fields are styled with a red * , but it is not validated if they are actually filled

This may lead to incorrect configuration settings in the authentication if you by accident miss one required field.