Upgrade documentation and configuration to newer PostgreSQL

[stranljip]

Prerequisites

• [X] Put an X between the brackets on this line if you have done all of the following:
  • Reproduced the problem.
  • Checked that your issue isn't already filed.
  • Filled the form.
  • Included logs and system information.

Description

When starting a setup with the provided docker-compose.yml everything starts as expected. However, Jira complains, that the database version is not supported. As of today, Atlassian states (https://confluence.atlassian.com/adminjiraserver/supported-platforms-938846830.html) that they support PostgreSQL 9.6 upwards to 11. The version 9.5 is no longer supported.

Steps to Reproduce

1. Fire up with docker-compose
2. Go through initial configuration steps for Jira
3. Go to https:///plugins/servlet/troubleshooting/view/ and look at "Instance Health" > "Supported Platforms" > "Supported database"

Expected behavior: I expect to see green check marks

Actual behavior: Jira complains, that PostgreSQL 9.5 is not supported

Reproduces how often: 100%

Versions

Logs And Environment Information

[jatty]

Perhaps we would need something like: https://devops.stackexchange.com/questions/10114/updating-software-in-a-docker-container