Fix undefined method `one?` when pushing to an existing merge request

Closes #45152

See merge request gitlab-org/gitlab-ce!18243

An untested code path was triggering an Exception because Fixnum
doesn't have `one?` implemented in Rails, while arrays and collections
do.

Closes #45152

The TIMESTAMP data type is used for values that contain both date and
time parts. TIMESTAMP has a range of '1970-01-01 00:00:01' UTC to
'2038-01-19 03:14:07' UTC.

A Forever lib class was included to handle future dates for PostgreSQL
and MySQL, also changes were made to DeployToken to enforce Forever.date

Also removes extra conditional from JwtController

- Adds a default on expires_at datetime
- Modifies deploy tokens views to handle default expires at value
- Use datetime_with_timezone where possible
- Remove unused scopes

Also, fixes broken specs

We use controller actions to pass a newly created token and errors

Also:
- Changes scopes from serializer to use boolean columns
- Fixes broken specs