[GNU ELPA] New package: url-http-oauth

[Thomas Fitzsimmons <fitzsim@fitzsim.org>]

Hi,

I would like to add one or two new packages to GNU ELPA.

The main one is url-http-oauth, which adds OAuth 2.0 support to the URL
library, via "url-auth" hooks, like url-http-basic, url-http-digest and
url-http-ntlm.  It provides auth-source integration for secrets, using
the netrc backend.

   https://git.sr.ht/~fitzsim/url-http-oauth

This package is unrelated to oauth2.el in GNU ELPA, which provides new
oauth2-url-retrieve and oauth2-url-retrieve-synchronously functions, and
has plstore instead of auth-source integration.  For Excorporate, I
needed something that would work with the built-in url-retrieve
functions and I couldn't see how to do that with oauth2.el.  I haven't
tested, but I see no reason that the two packages would interfere with
one another.

For the next release of Excorporate I want to depend on url-http-oauth
to fix the longstanding bug#50113, "Excorporate: Communicating with
domain that requires SSO?".  I have the changes ready; I am using them
daily.

The OAuth 2.0 standard encodes the use of a user-agent (i.e., web
browser) for authorization steps which differ per OAuth 2.0 provider,
and are not defined by the specification.  I have provided support for
package authors and users to write custom functions to automate these
web browser interactions in arbitrary ways:

   AUTHORIZATION-CODE-FUNCTION is an elisp function that takes an
   authorization URL as a string argument, and returns, as a string, a
   full URL containing a code value in its query string.

By default though, url-http-oauth will prompt the user to copy-n-paste
URLs to and from the web browser.  This is the most general default I
could think of; for example, this allows performing authorization in a
local web browser then pasting the result to an Emacs session running
three SSH hops away, where `browse-url' may not do the right thing.

Users and package authors can design automatic user-agent interactions,
but those ways are so varied that I wanted to see how they would evolve.
For example, I would like to see someone write an
authorization-code-function for Sourcehut that would use EWW inline.
For other OAuth 2.0 providers whose authorization steps require
JavaScript, EWW would not work.

I have published another, tiny package:

   https://git.sr.ht/~fitzsim/url-http-oauth-demo

It demonstrates the use of url-http-oauth against the Emacs-friendliest
OAuth 2.0 implementation I've found: Sourcehut.  Sourcehut's
implementation is entirely Free Software, and it does not require
JavaScript in the authorization steps.  Its client registration process
does not have onerous terms of use.  Any Sourcehut user should be able
to get url-http-oauth-demo working.  Maybe this package makes sense in
GNU ELPA, or perhaps it could be part of url-http-oauth's documentation.

I wrote these packages myself [1] and I have copyright assignment
paperwork on file.

Thomas

1. Except url-http-oauth--netrc-delete, which borrows lots of code from
   auth-source.el.