Initial integration of Archive Metadata in CTA

With the full archive metadata pipeline nearing completion, it is time to clearly define what we want our next steps to be w.r.t. integrating this into the CTA system.

• We need to pass along this metadata to the components of CTA (starting with the frontend). For this, we will need to define how we want to update the protobuf protocol we are using.
• We need to think about adding an additional test suite with tests related to archive metadata. This will be slightly complex due to the fact the HTTP PULL will need multiple instances. However, perhaps there is a way we can simplify or mimick this.

Further details will be added to this ticket as we progress. This ticket is meant as a general overview of what we want to do; specific tickets will be created for the different features.