Define rule instance table for Minder

Rule instances are currently stored as serialized protobuf structures in
the database, grouped by entity type. A separate join table exists to
track the relationship between a profile-entity and the rule types which
are used. This arrangement leads to some rather awkward code and
database queries making the profile-related code in Minder more complex
than it should be.

This PR adds in a definition of a dedicated rule instance table.
Subsequent PRs will migrate data over to it and then change the codebase
to query this table instead of the current tables.

database/migrations/000061_migrate_entity_profiles.down.sql

@@ -0,0 +1,16 @@
+-- Copyright 2024 Stacklok, Inc
+--
+-- Licensed under the Apache License, Version 2.0 (the "License");
+-- you may not use this file except in compliance with the License.
+-- You may obtain a copy of the License at
+--
+--      http://www.apache.org/licenses/LICENSE-2.0
+--
+-- Unless required by applicable law or agreed to in writing, software
+-- distributed under the License is distributed on an "AS IS" BASIS,
+-- WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+-- See the License for the specific language governing permissions and
+-- limitations under the License.
+
+-- Undoing the `up` query automatically is probably not a good idea.
+-- Leaving this as a no-op.

database/migrations/000061_migrate_entity_profiles.up.sql

@@ -0,0 +1,60 @@
+-- Copyright 2024 Stacklok, Inc
+--
+-- Licensed under the Apache License, Version 2.0 (the "License");
+-- you may not use this file except in compliance with the License.
+-- You may obtain a copy of the License at
+--
+--      http://www.apache.org/licenses/LICENSE-2.0
+--
+-- Unless required by applicable law or agreed to in writing, software
+-- distributed under the License is distributed on an "AS IS" BASIS,
+-- WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+-- See the License for the specific language governing permissions and
+-- limitations under the License.
+
+BEGIN;
+
+-- This backfills the rule_instances table using information about the rule
+-- instances stored in various tables in Minder.
+-- The migration query takes the following approach:
+--
+-- 1) Flatten each list of rules in the entity_profiles table by using
+--    JSONB_ARRAY_ELEMENTS() with a lateral cross join.
+--    This allows us to join each JSON object with the row in which it is stored.
+-- 2) Get the rule type ID by querying rule_type using name and project ID. The
+--    rule name comes from each JSON object. To get the project ID, we need to
+--    join entity_profiles to profiles on profile ID, and use the project_id
+--    column from profiles.
+--
+-- We also reuse the created_at timestamp from entity_profiles in rule_instances
+-- for the sake of consistency.
+
+INSERT INTO rule_instances (
+    profile_id,
+    entity_type,
+    rule_type_id,
+    name,
+    def,
+    params,
+    created_at
+)
+SELECT
+    ep.profile_id,
+    ep.entity AS entity_type,
+    rt.id AS rule_type_id,
+    cr->>'name' AS rule_name,
+    cr->'def' AS def,
+    cr->'params' AS params,
+    ep.created_at
+FROM entity_profiles AS ep
+    CROSS JOIN LATERAL JSONB_ARRAY_ELEMENTS(ep.contextual_rules) AS cr
+    JOIN profiles AS pf ON pf.id = ep.profile_id
+    JOIN rule_type AS rt ON rt.project_id = pf.project_id AND cr->>'type' = rt.name
+WHERE ep.migrated = FALSE;
+
+-- As of the previous PR, all new rows are written to both rule_instances and
+-- entities. By the time that we get to this part of the transaction, all rows
+-- will have been migrated.
+UPDATE entity_profiles SET migrated = TRUE;
+
+COMMIT;