deduplication of coordinate request parameters

[kaestli]

in wildcard expansion, we check caches of existing station- or channelepochs for existing epochs, and align endpoint requests to epoch borders, optimizing endpoint reverse proxy cache hits.
However, it seems we do not strip potentially available coordinate restrictions from requests, thus increasing request variability and reducing cache hits.

To Do:

• verify the issue, i.e. check whether there are still coordinates in endpoint requests
• make sure coordinate restrictions are evaluated in the wildcard expansion phase
• remove coordinate request parameters from endpoint requests.