This patchset expands on document uniquness in Deckhand which is
a bit involved.
At the **database** level, documents are uniquely identified by
the combination of:
#. ``metadata.name``
#. ``schema``
#. ``metadata.layeringDefinition.layer``
This means that raw revision documents -- which are persisted
in Deckhand's database -- require that the combination of all
3 parameters be unique.
However, **post-rendered documents** are only uniquely
identified by the combination of:
#. ``metadata.name``
#. ``schema``
Because collisions with respect to the the third parameter --
``metadata.layeringDefinition.layer`` -- can only occur with
replacement. But after document rendering, the replacement-parent
documents are never returned.
Change-Id: I841caa83bef46bf5e155136fbcd7444b672d06f8
d1b7ce154c