Rewrite Local Hub to Go

[pkosiec]

Description

• Consider https://github.com/dosco/graphjin
• Implement 1:1 features that we already support in Local Hub already
  vMake Local Hub to use PostgreSQL (Install Bitnami PostgreSQL Helm chart)
• Remember that in future we will extend it with multiple backends
• Do not support upgrade and migration from 0.5.0
• Extend TypeInstance GraphQL API with the TypeInstance.spec.backend field

Related issues

See epic #604 for reason and use cases.

[mszostok]

Investigations showed that rewriting doesn't make sense at the current stage, for more info check #626