Code review comment for lp:~dimitern/juju-core/103-relation-entity-tags

Reviewers: mp+180157_code.launchpad.net,

Message:
Please take a look.

Description:
state: Make Relation an Entity

This adds relation tags to the names package. The
format is "relation-<id>", where <id> is the relation's
numeric id.
It also adds a Tag() method on the relation, and a few
other necessary modifications to make state.Relation
objects behave like other entities. This is needed for
the uniter API facade, so relations can be used as
params and results.

https://code.launchpad.net/~dimitern/juju-core/103-relation-entity-tags/+merge/180157

Requires:
https://code.launchpad.net/~dimitern/juju-core/102-state-endpoint-refactoring/+merge/180141

(do not edit description out of merge proposal)

Please review this at https://codereview.appspot.com/12748044/

Affected files:
   A [revision details]
   A names/relation.go
   A names/relation_test.go
   M names/tag.go
   M names/tag_test.go
   M state/relation.go
   M state/state.go
   M state/state_test.go