Codebase Server API: Include metadata in `/getDefinition`

[hojberg]

Extend the /getDefinition codebase server API with metadata like author, license and data.

Completing this ticket will support this UI ticket: https://github.com/unisonweb/ui-core/issues/24

Suggested response

To the already existing /getDefinition API, add a metadata field with the following shape:

type Metadata {
  authors: List Author,
  copyrightHolders: List CopyrightHolder,
  licenses: List License
  createdAt: String, -- ISO 8601 formatted date time 
  updatedAt: String -- ISO 8601 formatted date time
}

❗This is dependent on https://github.com/unisonweb/unison/issues/2205

[pchiusano]

Revisit this after finalizing a design.

[hojberg]

Moved the design and JSON serialization specifics into its own ticket since it's needed for several other tickets: https://github.com/unisonweb/unison/issues/2205

Adjusted the RICE score accordingly

[mitchellwrosen]

#wontfix