Add external engine analysis post endpoints

[FriedrichtenHagen]

Checklist when adding a new endpoint

Building on @Anupyas PR I moved the analysis endpoints into the external_engine client. I handled the different base URL with a new parameter in the Requestor methods post and request which accepts the different base url.

• Added new endpoint to the README.md
• Ensure that my endpoint name does not repeat the name of the client. Wrong: client.users.get_user(), Correct: client.users.get()
• Typed the returned JSON using TypedDicts in berserk/types/, example
• Tested GET endpoints not requiring authentification. Documentation, example
• Added the endpoint and your name to CHANGELOG.md in the To be released section (to be created if necessary)

[fitztrev]

Could custom_base_url be overridden to test on a local dev site?

[FriedrichtenHagen]

Hi @fitztrev, I am not sure if I understand what you mean.
I believe the custom_base_url parameter is only necessary for the three new endpoints (analysis, aquire_request and answer_request). I am not aware of other endpoints that would need a base url that differs from the standard (https://lichess.org/). But I am new to this project, so please let me know if there is something I have overlooked.

[fitztrev]

I mean when someone goes to use berserk in a script, they are currently able to specify a custom base_url instead of pointing to production lichess.org.

See example here that points to http://nginx https://github.com/lichess-org/lila-docker/blob/main/scripts/berserk-example.py

[FriedrichtenHagen]

@fitztrev Yes, should be no problem. That custom base url would need to be passed as an argument (custom_base_url) when calling one of the new endpoints methods (analysis, aquire_request and answer_request).
The idea is to use this additional base url in addition to the main base url which is used by all other endpoints.

[benediktwerner]

I think it makes more sense to do it the same as with the tablebase or opening explorer where the custom URL can be set on the berserk.Client:

https://github.com/lichess-org/berserk/blob/master/berserk/clients/__init__.py#L91

https://github.com/lichess-org/berserk/blob/master/berserk/clients/tablebase.py

Unfortunately, some external engine requests have to go against the default Lichess URL but I think it also still makes sense to use a similar pattern with a separate client that has the correct base URL set instead of passing it on every call. The ExternalEngine client could create a separate sub-client in its constructor with the external engine URL as its base URL. Or ExternalEngine could simply not subclass BaseClient and instead have two clients as attributes. I think either option is fine.

Then we don't need custom URL params on any of the methods. And the default external engine URL can also be extracted to a constant at the top of the external engine file.

[FriedrichtenHagen]

@benediktwerner Thank you for the explanation, that makes sense and is indeed cleaner.
I have added a subclient as recommended and removed the use of custom_base_url. The external engine url is extracted to the top of the file.