chore: patch recent migration files that drop db columns (#5277)

# What this PR does

- patch recent migration files which drop several deprecated DB columns
which led to a recent (minor/internal) issue
- add a CI job to prevent this from happening in the future and instead,
force folks to drop columns [the _proper_
way](https://github.com/grafana/oncall/tree/dev/dev#removing-a-nullable-field-from-a-model)
(which we have documented internally)


(as documented
[here](https://github.com/grafana/oncall/tree/dev/dev#removing-a-nullable-field-from-a-model),
I have the four additional migration files (which actually do the `DROP
COLUMN`s in the db) saved locally, and will include these in a separate
PR/release)

## Checklist

- [x] Unit, integration, and e2e (if applicable) tests updated
- [x] Documentation added (or `pr:no public docs` PR label added if not
required)
- [x] Added the relevant release notes label (see labels prefixed w/
`release:`). These labels dictate how your PR will
    show up in the autogenerated release notes.

.github/workflows/linting-and-tests.yml

@@ -85,6 +85,59 @@ jobs:
           python manage.py makemigrations --check
           python manage.py lintmigrations
 
+  # the following CI check is to prevent developers from dropping columns in a way that could cause downtime
+  # (the proper way to drop columns is documented in dev/README.md)
+  #
+  # we've been bitten by this before (see https://raintank-corp.slack.com/archives/C081TNWM73N as an example)
+  ensure-database-migrations-drop-columns-the-correct-way:
+    name: "Ensure database migrations drop columns the correct way"
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout PR code
+        uses: actions/checkout@v3
+        with:
+          # Fetch all history so we can compare with the base branch
+          fetch-depth: 0
+          # Checkout the head commit of the PR
+          ref: ${{ github.event.pull_request.head.sha }}
+
+      - name: Fetch base branch
+        run: git fetch origin ${{ github.event.pull_request.base.ref }}:${{ github.event.pull_request.base.ref }}
+
+      - name: Check for RemoveField in Migrations
+        # yamllint disable rule:line-length
+        run: |
+          # Get the list of files changed in the PR
+          git diff --name-only ${{ github.event.pull_request.base.ref }}...${{ github.event.pull_request.head.sha }} > changed_files.txt
+
+          # Filter for migration files
+          grep -E '^.*/migrations/.*\.py$' changed_files.txt > migration_files.txt || true
+
+          # Initialize a flag
+          FAILED=0
+
+          # Check each migration file for 'migrations.RemoveField'
+          if [ -s migration_files.txt ]; then
+            while IFS= read -r file; do
+              echo "Checking $file for migrations.RemoveField..."
+              if grep -q 'migrations.RemoveField' "$file"; then
+                echo "❌ Error: Found migrations.RemoveField in $file"
+                FAILED=1
+              else
+                echo "✅ No RemoveField found in $file"
+              fi
+            done < migration_files.txt
+          else
+            echo "No migration files changed."
+          fi
+
+          # Fail the job if RemoveField was found
+          if [ "$FAILED" -eq 1 ]; then
+            echo "❌ Error: Found migrations.RemoveField in one or more migration files. Please check out our documentation at https://github.com/grafana/oncall/tree/dev/dev#removing-a-nullable-field-from-a-model on how to properly drop columns."
+            exit 1
+          fi
+        # yamllint enable rule:line-length
+
   unit-test-helm-chart:
     name: "Helm Chart Unit Tests"
     runs-on: ubuntu-latest-16-cores

engine/apps/alerts/migrations/0066_remove_channelfilter__slack_channel_id_and_more.py

@@ -12,14 +12,6 @@ class Migration(migrations.Migration):
 
     operations = [
         linter.IgnoreMigration(),
-        migrations.RemoveField(
-            model_name='channelfilter',
-            name='_slack_channel_id',
-        ),
-        migrations.RemoveField(
-            model_name='resolutionnoteslackmessage',
-            name='_slack_channel_id',
-        ),
         migrations.DeleteModel(
             name='AlertGroupPostmortem',
         ),

engine/apps/alerts/migrations/0067_remove_channelfilter__slack_channel_id_state.py

@@ -0,0 +1,18 @@
+# Generated by Django 4.2.16 on 2024-11-20 20:21
+
+import common.migrations.remove_field
+from django.db import migrations
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('alerts', '0066_remove_channelfilter__slack_channel_id_and_more'),
+    ]
+
+    operations = [
+        common.migrations.remove_field.RemoveFieldState(
+            model_name='channelfilter',
+            name='_slack_channel_id',
+        ),
+    ]

engine/apps/alerts/migrations/0068_remove_resolutionnoteslackmessage__slack_channel_id_state.py

@@ -0,0 +1,18 @@
+# Generated by Django 4.2.16 on 2024-11-20 20:23
+
+import common.migrations.remove_field
+from django.db import migrations
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('alerts', '0067_remove_channelfilter__slack_channel_id_state'),
+    ]
+
+    operations = [
+        common.migrations.remove_field.RemoveFieldState(
+            model_name='resolutionnoteslackmessage',
+            name='_slack_channel_id',
+        ),
+    ]

engine/apps/schedules/migrations/0020_remove_oncallschedule_channel.py → engine/apps/schedules/migrations/0020_remove_oncallschedule_channel_state.py

@@ -1,7 +1,7 @@
-# Generated by Django 4.2.16 on 2024-11-06 21:13
+# Generated by Django 4.2.16 on 2024-11-20 20:12
 
+import common.migrations.remove_field
 from django.db import migrations
-import django_migration_linter as linter
 
 
 class Migration(migrations.Migration):
@@ -11,8 +11,7 @@ class Migration(migrations.Migration):
     ]
 
     operations = [
-        linter.IgnoreMigration(),
-        migrations.RemoveField(
+        common.migrations.remove_field.RemoveFieldState(
             model_name='oncallschedule',
             name='channel',
         ),

engine/apps/user_management/migrations/0028_remove_organization_general_log_channel_id.py → engine/apps/user_management/migrations/0028_remove_organization_general_log_channel_id_state.py

@@ -1,7 +1,7 @@
-# Generated by Django 4.2.16 on 2024-11-06 21:11
+# Generated by Django 4.2.16 on 2024-11-20 17:58
 
+import common.migrations.remove_field
 from django.db import migrations
-import django_migration_linter as linter
 
 
 class Migration(migrations.Migration):
@@ -11,8 +11,7 @@ class Migration(migrations.Migration):
     ]
 
     operations = [
-        linter.IgnoreMigration(),
-        migrations.RemoveField(
+        common.migrations.remove_field.RemoveFieldState(
             model_name='organization',
             name='general_log_channel_id',
         ),