Some feeds have only the last X entries

[lemon24]

Use case:

1. Find a website via an article.
2. Want to add website feed to reader and mark that article as important.
3. Article does not appear in feed because feed contains only the last X articles, and the article fell off the end of the feed.

A possible solution is "share anything" articles (mentioned in https://github.com/lemon24/reader/issues/96#issuecomment-460077441), but for existing feeds.

Another solution might be to use the mechanism from #222 to backfill old articles.

[lemon24]

To do:

• [x] add a added_by entry attribute (feed, user etc.)
• [x] (maybe) add first_updated, so user entries can have updated none (#183 / https://github.com/lemon24/reader/issues/179#issuecomment-663840297)
  • renamed to added
• [x] add an add_or_update_entries()-like Reader method
  • it should likely be only "add" (no update, at least not by default)
  • requires exposing EntryData, and finding defaults for EntryUpdateIntent
  • [x] delete_entry() Reader method (only for entries added by add_entry())
• [ ] (maybe, later) way of extracting page content, maybe similar to #222
• [x] expose a limited version (id/link, title) in the web app
• [x] entry_dedupe interaction
• [x] tests
• [x] docs
• [x] changelog

[lemon24]

add_entry() mock-up: https://gist.github.com/lemon24/047f71abe76c47661634459eada7b50a

Based on thinking and talking with people about 00-api.py in the linked gist:

• it's nice to be able to pass an arbitrary Entry-like object
• creating a new object (dict or EntryData) is not too much of a bother
• requiring the user to build a new EntryData object adds some cognitive overhead
• the EntryData object should be mutable, which means neither reader.types.Entry nor reader._types.EntryData can inherit it

A Union[EntryDataLikeProtocol, EntryDataTypedDict] argument accommodates all of the above, and can (almost) be made to work with typing (example in 01-typing.py).

It may be a good idea to allow the nested types (Content, Enclosure) to be typed dicts as well (in 79a18c5). In cases like this, I'd like there to be a standard serialization library in Python (like Rust has Serde); maybe it's time to give mashumaro a try (https://github.com/lemon24/reader/issues/247#issuecomment-886022571).

[lemon24]

Decisions:

• add_entry(entry: Any), leave fancy typing for later
• user entries can't be updated
• delete_entry() only deletes user entries
• entry_dedupe doesn't distinguish between user and non-user entries (there may be undesired side-effects to this, but eh...)