Update the template to ask about data model changes

Changes which require modifications to the data model
often have a wider impact on the system.  The community
often has strong opinions on how the data model should
be evolved, from both a functional and performance
perspective, and disagreements and/or rework late in the
implemetaion stage are vrey disruptive and tiem consuming.
It is therefore important to capture and gain agreement
as early as possible on any proposed changes to the data
model.

Change-Id: I071043c7ce29bb8a47a9da9fb458befe91f6a609

specs/template.rst

@@ -54,6 +54,25 @@ What other ways could we do this thing? Why aren't we using those? This doesn't
 have to be a full literature review, but it should demonstrate that thought has
 been put into why the proposed solution is an appropriate one.
 
+Data model impact
+-----------------
+
+Changes which require modifications to the data model often have a wider impact
+on the system.  The community often has strong opinions on how the data model
+should be evolved, from both a functional and performance perspective. It is
+therefore important to capture and gain agreement as early as possible on any
+proposed changes to the data model.
+
+Questions which need to be addressed by this section include:
+
+- What new data objects and/or database schema changes is this going to require?
+
+- What Database migrations will accompany this change.
+
+- How will the initial set of new data objects be generated, for example if you
+  need to take into account existing instances, or modify other existing data
+  describe how that will work.
+
 REST API impact
 ---------------
 
@@ -121,8 +140,6 @@ such as:
   we have a special case in the code? Do we assume that the operator will
   recreate all the instances in their cloud?
 
-- Please specify expected Database migrations that accompany this change.
-
 Developer impact
 ----------------