Add URI-based file data support

[andrewheard]

Added support for URI-based file data (in addition to existing support for data as inline bytes). Files may be uploaded using the media.upload REST API.

[andrewheard]

cc: @paulb777 @rlazo

[rlazo]

Added support for URI-based file data (in addition to existing support for data as inline bytes). Files may be uploaded using the media.upload REST API.

Open Questions:

• URL or String for associated value type?

I'm ok with String unless strongly disliked

• uri vs. url? -- uri in REST API

I'd go with uri out of consistency with the underlying api

[andrewheard]

(https://ai.google.dev/api/rest/v1beta/media/upload) REST API.

Open Questions:

• URL or String for associated value type?

I'm ok with String unless strongly disliked

That sounds reasonable to me since it's also consistent with the underlying REST API.

• uri vs. url? -- uri in REST API

I'd go with uri out of consistency with the underlying api

SGTM. Since the type is now String, I've added a uri: label on the associated value to avoid ambiguity.