feature: edit / update workflow in data source details

[josh-chamberlain]

Context

requires:

• create and update endpoints for Data Sources #153
• Data Source Detail static view #18
• troubleshoot local Data Source Details link #151
• data source details visual refinements #150
• Users and login #24
• finalized wireframes for v2 of the app

We're about to get endpoints for creating and updating data sources. We should allow authenticated users to do that.

Requirements

• add an "edit" button to the data source details view
• generally, clicking "edit" should make editable fields (list tbd) editable, and a couple position: fixed "Save" / "Cancel" buttons should allow people to do those things
• non-auth'd users should not be able to see the edit button
• any non-auth'd user somehow loading the edit view should not be able to use the endpoint
• don't allow people to save without a submitter contact info, name, source_url, or empty access_type.
• changes need to push back to Airtable for now, until we replace it, or it will sync back old data.

Tests

• non-authenticated users should not be able to see the edit button
• non-auth'd users loading the edit view should not be able to save / use the endpoint

Docs

• tbd