Add flag to enable trust per repo (#2541)

* Add flag to enable trust per repo

* Add api for enabling/disabling trust

* Add new LogEntryKind for changing repo trust settings
Also add tests for repo trust api

* Add `set_trust` method to repository

* Expose new logkind to UI

* Fix registry tests

* Rebase migrations and regen test.db

* Raise downstreamissue if trust metadata can't be removed

* Refactor change_repo_trust

* Add show_if to change_repo_trust endpoint

data/migrations/versions/ed01e313d3cb_add_trust_enabled_to_repository.py

@@ -0,0 +1,34 @@
+"""Add trust_enabled to repository
+
+Revision ID: ed01e313d3cb
+Revises: c3d4b7ebcdf7
+Create Date: 2017-04-14 17:38:03.319695
+
+"""
+
+# revision identifiers, used by Alembic.
+revision = 'ed01e313d3cb'
+down_revision = 'c3d4b7ebcdf7'
+
+from alembic import op
+import sqlalchemy as sa
+
+def upgrade(tables):
+    ### commands auto generated by Alembic - please adjust! ###
+    op.add_column('repository', sa.Column('trust_enabled', sa.Boolean(), nullable=False))
+    ### end Alembic commands ###
+    op.bulk_insert(tables.logentrykind, [
+        {'name': 'change_repo_trust'},
+    ])
+
+
+def downgrade(tables):
+    ### commands auto generated by Alembic - please adjust! ###
+    op.drop_column('repository', 'trust_enabled')
+    ### end Alembic commands ###
+
+    op.execute(tables
+               .logentrykind
+               .delete()
+               .where(tables.
+                      logentrykind.name == op.inline_literal('change_repo_trust')))