support sharing of context with projects

[motatoes]

It would be great if digger provided a way of sharing additional variables with the workflow runs for use. The variables can be defined at the connected repo level and filtered based on various dimensions such as project name and so on. The variables can be optionally encrypted using a user's public key for secure sharing with the workflow.

User story

As a user I want an easy ui to manage repo-level values that are shared with the workflow by passing them down into the spec. I should be able to filter out the values based on project name (regex), or directory location of the project.

Use cases

• Sharing terraform-specific variables such as regions or keys in a secure way
• Sharing configuration for access of private modules on github or external registry
• Sharing non senitive tfvars with the runners
• An easier way compared to setting loads of github secrets and mapping them in the workflow