fix/airflow2-pgsql-mount: Fix Postgres volume mount and healthcheck for postgres:18-alpine+

Update mount point from /var/lib/postgresql/data to /var/lib/postgresql
and use $$POSTGRES_USER in pg_isready healthchecks to dynamically match
each service's configured user.

This fixes compatibility with postgres:18-alpine and later, following
the PGDATA relocation introduced in docker-library/postgres#1394.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: iobruno

module2-workflow-orchestration/airflow-2.x/compose.celery.yaml

@@ -52,9 +52,9 @@ services:
     ports:
       - '5432:5432'
     volumes:
-      - vol-ingest-db:/var/lib/postgresql/data
+      - vol-ingest-db:/var/lib/postgresql
     healthcheck:
-      test: ["CMD-SHELL", "pg_isready -U postgres"]
+      test: ["CMD-SHELL", "pg_isready -U $$POSTGRES_USER"]
       interval: 5s
       timeout: 5s
       retries: 5
@@ -70,9 +70,9 @@ services:
     ports:
       - '5432'
     volumes:
-      - vol-airflow-metastore-celeryexec:/var/lib/postgresql/data
+      - vol-airflow-metastore-celeryexec:/var/lib/postgresql
     healthcheck:
-      test: ["CMD-SHELL", "pg_isready -U postgres"]
+      test: ["CMD-SHELL", "pg_isready -U $$POSTGRES_USER"]
       interval: 5s
       timeout: 3s
       retries: 5

module2-workflow-orchestration/airflow-2.x/compose.local.yaml

@@ -46,9 +46,9 @@ services:
     ports:
       - '5432:5432'
     volumes:
-      - vol-ingest-db:/var/lib/postgresql/data
+      - vol-ingest-db:/var/lib/postgresql
     healthcheck:
-      test: ["CMD-SHELL", "pg_isready -U postgres"]
+      test: ["CMD-SHELL", "pg_isready -U $$POSTGRES_USER"]
       interval: 5s
       timeout: 5s
       retries: 5
@@ -64,9 +64,9 @@ services:
     ports:
       - '5432'
     volumes:
-      - vol-airflow-metastore-localexec:/var/lib/postgresql/data
+      - vol-airflow-metastore-localexec:/var/lib/postgresql
     healthcheck:
-      test: ["CMD-SHELL", "pg_isready -U postgres"]
+      test: ["CMD-SHELL", "pg_isready -U $$POSTGRES_USER"]
       interval: 5s
       timeout: 3s
       retries: 5