Use application_role_id on environment_roles.

In the future, an `application_invitation1 will not refer to a `user` until
someone accepts the invitation; they'll only reference an
`application_role`. When a user is invited to an application, the
inviter can specify the environments the invitee should have access to.
For this to be possible, an `environment_role` should reference an
`application_role`, because no `user` entity will be known at that time.

In addition to updating all the models and domain methods necessary for
this change, this commit deletes unused code and tests that were
dependent on `environment_roles` having a `user_id` foreign key.

alembic/versions/d2390c547dca_environment_roles_has_relation_to_.py

@@ -0,0 +1,54 @@
+"""environment_roles has relation to application_roles
+
+Revision ID: d2390c547dca
+Revises: ab1167fc8260
+Create Date: 2019-05-29 12:34:45.928219
+
+"""
+from alembic import op
+import sqlalchemy as sa
+from sqlalchemy.dialects import postgresql
+
+# revision identifiers, used by Alembic.
+revision = 'd2390c547dca'
+down_revision = 'ab1167fc8260'
+branch_labels = None
+depends_on = None
+
+
+def upgrade():
+    conn = op.get_bind()
+    op.add_column('environment_roles', sa.Column('application_role_id', postgresql.UUID(as_uuid=True), nullable=True))
+    op.drop_index('environments_role_user_environment', table_name='environment_roles')
+    op.create_index('environments_role_user_environment', 'environment_roles', ['application_role_id', 'environment_id'], unique=True)
+    op.drop_constraint('environment_roles_user_id_fkey', 'environment_roles', type_='foreignkey')
+    op.create_foreign_key("environment_roles_application_roles_fkey", 'environment_roles', 'application_roles', ['application_role_id'], ['id'])
+    conn.execute("""
+UPDATE environment_roles er
+SET application_role_id = application_roles.id
+FROM environments, applications, application_roles
+WHERE
+    environment_id = environments.id AND
+    applications.id = environments.application_id AND
+    application_roles.application_id = applications.id AND
+    er.user_id = application_roles.user_id;
+""")
+    op.alter_column('environment_roles', "application_role_id", nullable=False)
+    op.drop_column('environment_roles', 'user_id')
+
+
+def downgrade():
+    conn = op.get_bind()
+    op.add_column('environment_roles', sa.Column('user_id', postgresql.UUID(), autoincrement=False, nullable=True))
+    op.drop_constraint("environment_roles_application_roles_fkey", 'environment_roles', type_='foreignkey')
+    op.create_foreign_key('environment_roles_user_id_fkey', 'environment_roles', 'users', ['user_id'], ['id'])
+    op.drop_index('environments_role_user_environment', table_name='environment_roles')
+    op.create_index('environments_role_user_environment', 'environment_roles', ['user_id', 'environment_id'], unique=True)
+    conn.execute("""
+UPDATE environment_roles
+SET user_id = application_roles.user_id
+FROM application_roles
+WHERE application_role_id = application_roles.id
+""")
+    op.alter_column('environment_roles', "user_id", nullable=False)
+    op.drop_column('environment_roles', 'application_role_id')