Support search in OPDS

[llemeurfr]

Equivalent to the OPDS search in the iOS app.

[mickael-menu]

@llemeurfr What did you have in mind for the OPDS search support in r2-opds-kotlin?

[llemeurfr]

It's an old issue, seems partially solved at the OPDS parsing level: I see code in OPDS1Parser.kt about a link with rel=search, but none about search in OPDS2Parser.kt.

Could you please check that the parser exposes a search API method in both cases, and later (other issue) that R2 Reader uses this API to expose the search feature to users? which in fact is not the case for R2 Reader iOS nor Android; I just checked with the OPDS 1 Feedbooks catalog.

[mickael-menu]

No it's not implemented at the moment, so to summarize we need:

• A helper to get the search link from a query at the Publication level.
• (Maybe) A helper at the Feed/Parser level to perform the search query on behalf of the app, using the previous link helper.
• A sample implementation in the test apps.