ansible/hg-web: enable wire protocol version 2 (bug 1505557); r=sheehan

This is a prerequisite using the new partial clone implementation in
Mercurial 4.8.

Ideally we'd have test coverage for this. I reckon I'll implement tests
later as part of teaching robustcheckout how to deal with things. For
now, let's get this deployed so we can start testing wireprotov2
clients against the server.

Merely enabling the feature shouldn't have any other effect on the
server and existing client interactions other to expose the new API
endpoint.

Differential Revision: https://phabricator.services.mozilla.com/D11404

--HG--
extra : moz-landing-system : lando

ansible/roles/hg-web/templates/hgrc.j2

@@ -91,6 +91,10 @@ bugzilla = s|((?:bug[\s#]*|b=#?|#)(\d{4,}))|<a href="https://bugzilla.mozilla.or
 # this limit.
 httppostargs = true
 
+# Wire protocol v2 support.
+web.apiserver = true
+web.api.http-v2 = true
+
 [obshacks]
 # Enable the user that runs hgweb and performs replication to exchange
 # obsolescence markers, even if not enabled for regular users.