Add support for self-updating secrets

[its-felix]

Add support for secrets that change upon use.

I'm running a oauth2-server and would like to monitor the uptime of the token endpoint. Since the refresh-token changes with every token refresh, this requires a new secret after every invocation.

Example

Example Request

POST /oauth2/token
Content-Type: application/x-www-form-urlencoded

client_id=XYZ&client_secret=SECRET&grant_type=refresh_token&refresh_token=VOLATILE_SECRET

Example Response

{
    "access_token": "...",
    "refresh_token": "THIS WOULD NEED TO BE SAVED AS THE NEW VOLATILE_SECRET",
    "scope": "...",
    "token_type": "Bearer",
    "expires_in": 1795
}

Note

• This could partially be solved by using a more feature-rich HTTP-Client like https://www.jetbrains.com/help/idea/http-client-cli.html (https://www.jetbrains.com/help/idea/http-response-handling-examples.html#script-var-example)
• This would of course require a PAT with write permissions to repository secrets.

[its-felix]

Similar to https://github.com/orgs/upptime/discussions/446