Improve merge support for records with no uuid

for now we "pretend" they have a uuid still, custom view is
responsible for determining the value for each row if needed

tailbone/grids/core.py

@@ -170,6 +170,21 @@ class Grid(object):
                   'myfield': myrender,
               },
           )
+
+    .. attribute row_uuid_getter::
+
+       Optional callable to obtain the "UUID" (sic) value for each
+       data row.  The default assumption as that each row object has a
+       ``uuid`` attribute, but when that isn't the case, *and* the
+       grid needs to support checkboxes, we must "pretend" by
+       injecting some custom value to the ``uuid`` of the row data.
+
+       If necssary, set this to a callable like so::
+
+          def fake_uuid(row):
+              return row.some_custom_key
+
+          grid.row_uuid_getter = fake_uuid
     """
 
     def __init__(self, key, data, columns=None, width='auto', request=None,
@@ -182,7 +197,7 @@ class Grid(object):
                  sortable=False, sorters={}, default_sortkey=None, default_sortdir='asc',
                  pageable=False, default_pagesize=None, default_page=1,
                  checkboxes=False, checked=None, check_handler=None, check_all_handler=None,
-                 checkable=None,
+                 checkable=None, row_uuid_getter=None,
                  clicking_row_checks_box=False, click_handlers=None,
                  main_actions=[], more_actions=[], delete_speedbump=False,
                  ajax_data_url=None, component='tailbone-grid',
@@ -243,6 +258,7 @@ class Grid(object):
         self.check_handler = check_handler
         self.check_all_handler = check_all_handler
         self.checkable = checkable
+        self.row_uuid_getter = row_uuid_getter
         self.clicking_row_checks_box = clicking_row_checks_box
 
         self.click_handlers = click_handlers or {}
@@ -1425,6 +1441,16 @@ class Grid(object):
             })
         return columns
 
+    def get_uuid_for_row(self, rowobj):
+
+        # use custom getter if set
+        if self.row_uuid_getter:
+            return self.row_uuid_getter(rowobj)
+
+        # otherwise fallback to normal uuid, if present
+        if hasattr(rowobj, 'uuid'):
+            return rowobj.uuid
+
     def get_buefy_data(self):
         """
         Returns a list of data rows for the grid, for use with Buefy table.
@@ -1481,8 +1507,9 @@ class Grid(object):
 
             # maybe add UUID for convenience
             if 'uuid' not in self.columns:
-                if hasattr(rowobj, 'uuid'):
-                    row['uuid'] = rowobj.uuid
+                uuid = self.get_uuid_for_row(rowobj)
+                if uuid:
+                    row['uuid'] = uuid
 
             # set action URL(s) for row, as needed
             self.set_action_urls(row, rowobj, i)