Manually upgrade PostgreSQL in Geo HA from 9.6.14 to 10.9 using GitLab version 12.2.8

Problem to solve

Due to omnibus-gitlab#4705 (closed) the PostgreSQL database was not updated on the Geo HA cluster.

Proposal

• Manually upgrade the Geo HA cluster from 9.6.14 to 10.9
• Record steps taken
• Record any issues
• Verify that PostgreSQL version is upgraded as expected
• Decide if additional documentation is needed