[CT-1989] Parse group resource

[MichelleArk]

Parse a group resource as defined in schema yml files. Groups have a required (at least for now!) owner that should be unified with the existing ExposureOwner dataclass internally.

Example spec:

# models/marts/github/github.yml

groups:
  - name: github
    owner: 
      name: Jeremy
      email: data@jer.co
      slack: talk-jerco-memes
      github: jtcohen6
      whatever: you want

Eventually (issue), group names will be used as values for the optional group model config:

# models/marts/github/github.yml

models:
  - name: int__github_issue_label_history
    config: 
      group: github  # explicit opt-in
  - name: fct_github_issues
    config: 
      group: github  # explicit opt-in

Considerations

• ExposureOwner currently has a required email, and an optional name. What should the unified unparsed Owner schema be? Proposal for a unified schema/dataclass in [CT-1999] Unify ExposureOwner dataclass with group Owner #6833