[web] set proper Cache-Control header for static files - set Cache-Control max-age to match Expires - use the max_age method (defaults to 1 week) instead of hardcoded 6 months

[web] use a redirect for /data/foo requests that don't use the instance md5 hash The actual file contents can be cached for a long time. If the request doesn't use the hash, that's wrong. Using a redirect lets keep the caching for the actual file contents while not breaking requests missing the hash.

[web] fix typo in doc string

[web] stop adding an Expires header with all responses As per RFC 1945 (HTTP 1.0): If the date given is equal to or earlier than the value of the Date header, the recipient must not cache the enclosed entity. As per RFC 7234 (HTTP 1.1 Caching): If a response includes a Cache-Control field with the max-age directive (Section 5.2.2.8), a recipient MUST ignore the Expires field. Bottom line, the Expires header is now handled wherever the Cache-Control is handled: inside cache managers.

[web] stop looking at a request's Cache-Control header As per RFC 7234 (HTTP 1.1 Caching): The "Cache-Control" header field is used to specify directives for caches along the request/response chain. CubicWeb is not a cache.

[fti] add cw_fti_index_rql_limit method Improves on and deprecate cw_fti_index_rql_queries: execute the rql directly, so that we don't need to compute the set of eids up-front, but can just keep track of the last seen entity. Use the new method in reindex_entities. Keep calling cw_fti_index_rql_queries if it has been redefined (e.g in cubes). Related to #3621392.