WIP External Account Binding (#6059)

* Rough draft of External Account Binding.

* Remove parameter --eab and namespace kid and hmac. Also add parameters to "register" subcommand.

* Refactor as much as possible of the EAB functionality into ExternalAccountBinding class.

* Remove debug line.

* Added external account binding to Directory.Meta.

* Rename to account_public_key, hmac_key and make some non-optional.
Rename command line argument to --eab-hmac-key.

* Error out when the server requires External Account Binding and the user
has not supplied kid and hmac key.

* Remove whitespace.

* Refactor a bit to make it possible to set the url argument.

* Move from_data method into client.

* Revert "Move from_data method into client."

This reverts commit 8963fae

* Refactored to use json field on Registration.

* Inherit from object according to Google Python Style Guide.

* Move to two separate ifs.

* Get tests to pass after External Account Binding additions.

* messages.py back to 100% test coverage with some EAB tests.

* .encode() this JSON key.

* Set eab parameter default values to None.

* * Remove unnecessary public key mock on most of the test.
* Restructure the directory mock to be able to mock both True and False for externalAccountRequired easily.
* Add EAB client tests.

* Move external_account_required check into BackwardsCompatibleClientV2 to be able to mock it.

* Update versions.

* Try 0.29.0.

* Revert "Try 0.29.0."

This reverts commit 5779509

* Try 0.29.0 again.

* Try this.

* Fix pylint failures.

* Add tests for external_account_required method.

* Test not needed, avoid:
************* Module acme.client_test
C:  1, 0: Too many lines in module (1258/1250) (too-many-lines)

* Move real external_account_required method into ClientV2 and pass through to it in BackwardsCompatibleClientV2.

* Handle missing meta key in server ACME directory.

* Add docstring for BackwardsCompatibleClientV2.external_account_required().

* Add tests for BackwardsCompatibleClientV2.external_account_required().

* Fix coverage for ACMEv1 code in BackwardsCompatibleClientV2.

* Disable pylint too-many-lines check for client_test.py.

* Fix versions.

* Remove whitespace that accidently snuck into an earlier commit.

* Remove these two stray whitespaces also.

* And the last couple of whitespaces.

* Add External Account Binding to changelog.

* Add dev0 suffix to setup.py.

Co-Authored-By: robaman <robert@kastel.se>

* Set to "-e acme[dev]" again.

Co-Authored-By: robaman <robert@kastel.se>

CHANGELOG.md

@@ -9,6 +9,8 @@ Certbot adheres to [Semantic Versioning](http://semver.org/).
 * Noninteractive renewals with `certbot renew` (those not started from a
   terminal) now randomly sleep 1-480 seconds before beginning work in
   order to spread out load spikes on the server side.
+* Added External Account Binding support in cli and acme library.
+  Command line arguments --eab-kid and --eab-hmac-key added.
 
 ### Changed