Add issued handlers to auth_ref and fixtures

issued_at is a standard part of V2 and V3 tokens so add it to
AccessInfo in a similar way to expiry. Also it should be included when
generating tokens so include it in fixtures.

Change-Id: I0d62d8ce6472466886751e10e98046b8e398e079
Session Adapters

A Session is a global object that can be shared around. There are
however many variables (those passed to session.request) that are
specific to the client that will be using that session. These often need
to be set for every request going through a client.

For this purpose we have a Session Adapter. An adapter is like a
view on a session. Where the session maintains very global state the
adapter maintains state relevant to a specific usage of a session. These
might be things like User-Agent which wants to be set per client using
the session, or possibly even auth plugins if we share a common session
object amongst a number of clients with different plugins.

Almost anything that gets passed to a Session.request() call is suitable
to go into an adapter (the exceptions are essentially the body data and
method which only makes sense per call)

Implements: blueprint session-propagation
Change-Id: I100c791806674213d3cdb5389d4b0a1cf88c82dd
Make parameters in EndpointManager optional

Change adminurl and internalurl parameters in EndpointManager create()
to optional parameters.

Change-Id: I490e35b89f7ae7c6cdbced6ba8d3b82d5132c19d
Closes-Bug: #1318436
Correcting using-api-v2.rst

Changes
* removed extraneous word from Introduction section

Closes-Bug: #1334915
Change-Id: I201ddb70a4d91e0d615e322abc43848993dee573
Merge "Session Adapters"
Merge "Make parameters in EndpointManager optional"
Updated from global requirements

Change-Id: Ibb290d0f2d616b7730914bfc829a7f555ba0b688
Minor grammatical fix in doc

Change-Id: I0ee386588ab3083d90c5da44337460e39fa86e83
Closes-Bug: #1334915
Merge "Add issued handlers to auth_ref and fixtures"
Merge "Correcting using-api-v2.rst"
Merge "Minor grammatical fix in doc"