add configurable blacklist for all URL endpoints

[janl]

with help from @iilyak, thanks!

[kxepal]

How to use it?

[rnewson]

throw({not_found, "The URL to send a 404?

[kxepal]

+1

[iilyak]

Please select different value for error so it matches one of the clauses here:
https://github.com/apache/couchdb-chttpd/blob/master/src/chttpd.erl#L715
Possible options are:

• https://github.com/apache/couchdb-chttpd/blob/master/src/chttpd.erl#L729
• https://github.com/apache/couchdb-chttpd/blob/master/src/chttpd.erl#L737

[rnewson]

I was aiming for;

error_info({not_found, Reason}) ->
{404, <<"not_found">>, Reason};