Add support for chain filter

[hoh]

Users cannot filter messages based on the chain message field.

Suggestion:

src/aleph/web/controllers/messages.py --- 1/2 --- Python
46 46 
47 47     filters: List[Dict[str, Any]] = []
48 48     addresses = get_query_list_field("addresses")
.. 49     chains = get_query_list_field("chains")
49 50     refs = get_query_list_field("refs")
50 51     content_types = get_query_list_field("contentTypes")
51 52     channels = get_query_list_field("channels")

src/aleph/web/controllers/messages.py --- 2/2 --- Python
68 69             }
69 70         )
.. 71 
.. 72     if chains is not None:
.. 73         filters.append({"chain": {"$in": chains}})
70 74 
71 75     if content_keys is not None:
72 76         filters.append({"content.key": {"$in": content_keys}})

Related to aleph-im/aleph-message#7

[odesenfans]

Resolved by #282.