branch_heads table has no primary key (Postgres)

[dheardal]

Pre issue-raising checklist

I have already (please mark the applicable with an x):

• Upgraded to the latest Pact Broker OR
• Checked the CHANGELOG to see if the issue I am about to raise has been fixed
• Created an executable example that demonstrates the issue using either a:
  • Dockerfile
  • Git repository with a Travis or Appveyor (or similar) build

Software versions

• pact-broker docker version: eg 2.112.0

Expected behaviour

branch_heads should have a primary key.

Actual behaviour

branch_heads does not have a primary key.

This causes issues for us as we use logical replication on our postgres instances but it is not possible without a primary key defined on the table.