For the testing period, Electron and Proton were running in parallel and in RESTBase the traffic was split between them. For quite some time now Proton was receiving 100% of the traffic electron receives, but the resulting PDF was still served from Electron unless a special query parameter was provided.

This behavior is controlled with 'new_probability' config parameter in RESTBase to switch traffic to Proton step-by-step. Now it's time to start getting rid of Electron, so we'd need to make the default result returned to the user use Proton. I do not think that making probabilistic returns from either one or another makes any sense as it would be confusing, so let's just simplify the PDF RESTBbase module, so that it can only talk to Proton and simplify the config. In case the users will complain about the output we can just roll back the patch.

After some time, when we're sure the new output is good, we need to expand RESTBase API for the PDF endpoint with additional optional parameters that Proton supports.

This task has 2 parts:

• Switch all traffic to Proton and start serving Proton content by default
• Expand RESTBase API to support additional parameters that Proton added.