[CT-2200] Model view: when available, display model owner in dbt-docs

[MichelleArk]

In the model view (/model/{model_id}) of dbt-docs, display the model owner (by name?) when available.

If a model is part of a group, its owner information should be available as part of the group property.

[emmyoop]

If a model has a group, it will have an owner. If it's not in a group and doesn't have an owner then use the value we use today (from WH).

Will require looking up the owner as defined in the group.

[emmyoop]

What is the owner? Do we want to add a field per owner type(name, email, slack, etc)? Have some kind of ranking? Use name is available, then email, then... and if none are available use the warehouse value.

Exposures currently list both the owner name and the owner email and dynamically hide one if it's not available.

[aranke]

I've been confused by the owner object in the past, so here are my 2c:

1. Flatten it to a Git-style simple string User <user@domain.com>.
2. Keep it simple, Slack/GitHub/other social handles are overkill.