This is a lightweight placeholder so calendar functionality can be
tested. Simply presents a message about the invitation, and a set of
yes/maybe/no buttons to click.
The UI is shown whenever the message appears to contain an invite.
There are many elements left to be done here:
TODO: response code (EAS protocol) doesn't seem to work
TODO: use real assets & design
TODO: provide a click-link into calendar event
TODO: show calendar icon in messagelist too
TODO: (if possible) persist user's response in button state?
* Shown next to subject (non-final layout)
* Value taken from provider data
* Tapping star toggles state
* State writes back to provider
NOTE: I am currently doing the provider writeback via direct provider
calls (using the synced-message URI) but not doing it with a service call,
so at this point there is no triggering of any server-side update.
However a sync engine might "discover" the change.
NOTE: I made a global change of "mMessage" to "mOldMessage" because
there is still a lot of legacy code in MessageView and I wanted to clearly
demarcate the code that still needs to be redone.
