Wallabag: Add API endpoint for app name

[Strubbl]

Issue details

Currently wallabag Android app detects if a given URL is really a wallabag site by parsing the URL's source code and searching for some strings. This is an ugly solution. Errors occur like: https://github.com/wallabag/android-app/issues/744

It would be awesome if we can have an API endpoint which only tells what kind of application this is. E.g.

/api/applicationname returns only "wallabag"

I have thought about /api/version, but that does might be duplicate with other applications on the planet.

Environment

• wallabag version (or git revision) that exhibits the issue: 2.3.4 (and before)
• How did you install wallabag? Via git clone or by downloading the package? git
• Last wallabag version that did not exhibit the issue (if applicable): none
• php version: 7.0
• OS: debian
• type of hosting (shared or dedicated): dedicated
• which storage system you choose at install (SQLite, MySQL/MariaDB or PostgreSQL): pg

[j0k3r]

Why not create a better version endpoint?
As of now we have api/version returning a plain version string. Which is a really bad idea because we can't add new stuff to that enpoint. Anyway.

Can't we introduce a /api/info (or an other name) returning something like:

{
    "appname": "wallabag",
    "version": "2.4.0-dev",
    "allowed_registration": false
}