This PR removes the `OAuthContextSettings` class, and makes the `--oauth-url` option available on each backend that uses it, so it can be configured as part of the destination.
To assemble everything related to configuring OAuth, the code was moved to the `AuthIdOptionsHelper`, such that the usage can be shared between implementations.
This PR also adds the option to set the default OAuth url from the environment variable `DUPLICATI_OAUTH_SERVICE`.
The server can then be set in the following locations (most important last):
- Environment variable
- Server-wide advanced settings
- Backup job advanced settings (or commandline)
- Destination url
This class extends HttpClient and uses an OAuthHttpMessageHandler under the covers to automatically authenticate requests.
Additionally, it automatically respects the global HttpContextSettings for overall timeout, read/write timeout, and SSL certificate validation.
(BufferRequests isn't currently handled, as HttpClient doesn't seem to easily expose that flag, and as of .NET 4.5, seems to not buffer by default.)
This class implements the abstract HttpMessageHandler class (mostly via the default HttpClientHandler implementation).
This abstract class is used by System.Net.Http.HttpClient as the underlying HTTP mechanism, and in this particular case is used to automatically add an authorization header to each request.
It also provides a method for marking a request as one that should not be authenticated.
Kenneth Skovhede