* add Postgresql client certificate authentication option
* user(robots): disallow robot login and create PROJQUAY-5968
Add a config flag `ROBOTS_DISALLOW` to turn off Robot login and creation
in Quay for all accounts.
with the Flag set existing Robots cannot login anymore
```
$ podman login -u milang+test2 -p W7B...HQA quay.example.com
Error: logging into "quay.example.com": invalid username/password
```
This behavior will be reported in the logs accordingly
```
gunicorn-registry stdout | 2023-08-24 19:08:01,907 [253] [WARNING] [auth.credentials] Failed to validate credentials for robot milang+test2: Robot account has been disabled. Please contact your administrator.
```
as well as in the UI when creating a Robot Account which will display
the `Robot account has been disabled. Please contact your
administrator.` message.
* Revert "add Postgresql client certificate authentication option"
need to branch for PR (stupid me)
This reverts commit f8f54eead2.
* fixed error message to proper english and added schema definition for the option
67028af9e2