Create PostgreSQL extensions conditionally.

This is because in Azure PostgreSQL Flexible Server v15, ordinary users (without
the azure_pg_admin role) cannot create extensions. These extensions need to be
created before deploying this service into the cloud.

src/main/resources/db/migration/V2__init_schemas.sql

@@ -2,6 +2,35 @@ CREATE SCHEMA infrastructure_network;
 
 CREATE SCHEMA network;
 
-CREATE EXTENSION IF NOT EXISTS pgcrypto;
+-- Create extension conditionally. This is because in Azure PostgreSQL Flexible
+-- Server v15, ordinary users (without the azure_pg_admin role) cannot create
+-- extensions. These extensions need to be created before deploying this service
+-- into the cloud.
 
-CREATE EXTENSION IF NOT EXISTS btree_gist;
+-- Conditionally create the btree_gist extension.
+DO $$
+DECLARE
+    ext_exists BOOLEAN;
+BEGIN
+    -- Check if btree_gist extension exists.
+    SELECT EXISTS (SELECT 1 FROM pg_extension WHERE extname = 'btree_gist') INTO ext_exists;
+
+    -- Create extension only if it doesn't exist.
+    IF NOT ext_exists THEN
+        CREATE EXTENSION IF NOT EXISTS btree_gist SCHEMA public;
+    END IF;
+END $$;
+
+-- Conditionally create the pgcrypto extension.
+DO $$
+DECLARE
+    ext_exists BOOLEAN;
+BEGIN
+    -- Check if pgcrypto extension already exists.
+    SELECT EXISTS (SELECT 1 FROM pg_extension WHERE extname = 'pgcrypto') INTO ext_exists;
+
+    -- Create extension only if it doesn't exist.
+    IF NOT ext_exists THEN
+        CREATE EXTENSION IF NOT EXISTS pgcrypto SCHEMA public;
+    END IF;
+END $$;