Provide prometheus metrics

[noahingh]

We should provide metrics about the Gitploy application that users can manage Gitploy themselves. In the issue, we'll consider 1) which metrics are being and 2) how to implement them.

Metrics

• The response code of the server
• The count of repositories
• The count of deployment of repository for each environment (e.g. dev, production), respectively
• The count of user
• The limit of user