Metadata needs to be indexed

[stakach]

currently a simple metadata search locks up the database due to high CPU when there are 1000's of records (client with 24k records sees a 5minute denial of service)

Thinking we move metadata over to postgresql soon #165
possibly as part of staff api which also has metadata and some change hooks into rethinkdb, reverting the metadata field in rethink back to text

Then search operations can occur on staff API against a postgresql GIN index
https://cgi.cse.unsw.edu.au/~cs9315/20T1/postgresql/documentation/functions-json.html
https://medium.com/hackernoon/how-to-query-jsonb-beginner-sheet-cheat-4da3aa5082a3