Consider Origin & Share metadata conditional queries in the filtering

[dimstav23]

Current filtering rules:

• We perform the filtering based on the user key and conditional user key provided in the default policy or query respectively.
  They have to be present either as the user owner or in the shared users set.
• We examine whether all the purposes are in the purpose set of the KV pair.
• We examine whether none of the purposes is in the objection set of the KV pair.
• We examine the expiration time of the KV pair.
• We check whether logging is required for the KV pair.

Future rules (if needed):

• Check the conditional origin provided in the query or in the default policy. This implementation currently is commented out as it's really restrictive. Origin is a single string value.
• Check for the matching of the shared users set, either provided by the default policy or as a conditional query parameter. Shared metadata field accepts multiple values. TBD: The provided (conditional or default) values should be subset of the KV pair shared set or they should match exactly?
• Check the conditional objection (objObjectionIs) parameter. For now, since we are based on purposes, it doesn't really make sense.