Postgres 16 upgrade documentation (#4651)

Added documentation for upgrading Postgres and TimescaleDB to the latest version

docs/source/postgres_upgrade.rst

@@ -0,0 +1,51 @@
+Upgrade a SEED database from Postgres 12 to Postgres 16
+=======================================================
+
+Assumptions
+-----------
+
+- This process assumes that you're currently using Postgres 12.7 with TimescaleDB 2.3.0 from ``timescale/timescaledb-postgis:2.3.0-pg12`` or ``timescale/timescaledb-postgis:latest-pg12``
+- This also assumes that you have a directory in the host filesystem, e.g. ``~/share``, that is bind mounted to ``/share`` in your existing database container
+
+1. Create a dump of the current database
+
+.. code-block:: bash
+
+   docker exec seed_postgres pg_dump -d seed -U seeduser -Fc -f /share/seed-pg12.dump
+
+2. Create a temporary Postgres 13 container using the Docker image ``timescale/timescaledb-ha:pg13.14-ts2.14.2-oss``
+
+.. code-block:: bash
+
+   docker run --rm --name=seed-pg13 -e POSTGRES_DB=seed -e POSTGRES_USER=seeduser -e POSTGRES_PASSWORD=password -v ~/share:/share timescale/timescaledb-ha:pg13.14-ts2.14.2-oss
+
+Once the container has finished initializing, open a separate shell
+
+.. code-block:: bash
+
+   docker exec -it seed-pg13 bash
+   psql -d seed -U seeduser -c "CREATE EXTENSION postgis;"
+   psql -d seed -U seeduser -c "DROP EXTENSION timescaledb;"
+   psql -d seed -U seeduser -c "CREATE EXTENSION timescaledb WITH VERSION '2.3.0';"
+   psql -d seed -U seeduser -c "SELECT timescaledb_pre_restore();"
+   pg_restore -d seed -U seeduser /share/seed-pg12.dump
+   psql -d seed -U seeduser -c "SELECT timescaledb_post_restore();"
+   psql -d seed -U seeduser -c "ALTER EXTENSION timescaledb UPDATE;"
+   pg_dump -d seed -U seeduser -Fc -f /share/seed-pg13.dump
+
+3. Start the new, permanent Postgres 16 container using the Docker image ``timescale/timescaledb-ha:pg16.2-ts2.14.2-oss``
+
+.. code-block:: bash
+
+   docker run -d --name=seed-pg16 -e POSTGRES_DB=seed -e POSTGRES_USER=seeduser -e POSTGRES_PASSWORD=password -v ~/share:/share timescale/timescaledb-ha:pg16.2-ts2.14.2-oss
+
+Once the container has finished initializing, open a separate shell
+
+.. code-block:: bash
+
+   docker exec -it seed-pg16 bash
+   psql -d seed -U seeduser -c "CREATE EXTENSION postgis;"
+   psql -d seed -U seeduser -c "SELECT timescaledb_pre_restore();"
+   pg_restore -d seed -U seeduser /share/seed-pg13.dump
+   psql -d seed -U seeduser -c "SELECT timescaledb_post_restore();"
+   pg_dump -d seed -U seeduser -Fc -f /share/seed-pg16.dump