Remove support for Reach provider

This provider was never active and support was never completed, so
there's little value in keeping all this potentially confusing code.

migrations/versions/0370_remove_reach.py

@@ -0,0 +1,54 @@
+"""
+
+Revision ID: 0370_remove_reach
+Revises: 0369_update_sms_rates
+Create Date: 2022-04-27 16:00:00
+
+"""
+import itertools
+import uuid
+from datetime import datetime
+
+from alembic import op
+from sqlalchemy.sql import text
+
+from app.models import LetterRate
+
+
+revision = '0370_remove_reach'
+down_revision = '0369_update_sms_rates'
+
+
+def upgrade():
+    conn = op.get_bind()
+    conn.execute("DELETE FROM provider_details WHERE identifier = 'reach'")
+
+
+def downgrade():
+    conn = op.get_bind()
+    conn.execute(
+        """
+        INSERT INTO provider_details (
+            id,
+            display_name,
+            identifier,
+            priority,
+            notification_type,
+            active,
+            version,
+            created_by_id
+        )
+        VALUES (
+            '{}',
+            'Reach',
+            'reach',
+            0,
+            'sms',
+            false,
+            1,
+            null
+        )
+        """.format(
+            str(uuid.uuid4()),
+        )
+    )