feat: Implement Onboarding features

[NeloBlivion]

Summary

Construction hammered a hole through my ceiling and woke me up way too early so i implemented onboarding, probably.

• All relevant types and enums
• GET endpoint - await guild.onboarding()
• PUT endpoint - await Onboarding.edit(...) or await guild.edit_onboarding(...) to avoid multiple requests
• Updated some audit log events

References:

• [onboarding] Adds initial docs for Onboarding API discord/discord-api-docs#5915
• Adds docs for Onboarding updates and new mode field discord/discord-api-docs#6101
• Support Onboarding and Server Guide in Audit Log Events discord/discord-api-docs#6041

There is some jank due to this feature still being incomplete(?), but everything should be working. Probably needs more review due to inconsistent typing and lack of knowledge on the endpoint (emoji??).

• You can edit onboarding even if you aren't in a community server
• All OnboardingPrompts and PromptOptions require a (sometimes unique) snowflake to edit even if created by the user, but it can be any value; since it isn't relevant for the user to submit one, randint (lol) will be used when not supplied.

Example: Adding a prompt to an existing onboarding flow

flow = await guild.onboarding()
prompts = flow.prompts
new_prompt = OnboardingPrompt(
    title="Pick a colour!",
    required=True,
    single_select=True,  # Single vs. multiple choice
    in_onboarding=False,  # Don't show to user on join
    options=[
        PromptOption(title="Red", emoji="🍎", roles=[guild.get_role(RED_ROLE_ID)]),
        PromptOption(title="Blue", description="water", channels=[guild.get_channel(BLUE_CHANNEL_ID)])
    ]
)
prompts.append(new_prompt)
await flow.edit(prompts=prompts)

Perhaps it would be beneficial to add further functions out of the API scope like Onboarding.add_prompt etc. etc.

Information

• This PR fixes an issue.
• This PR adds something new (e.g. new method or parameters).
• This PR is a breaking change (e.g. methods or parameters removed/renamed).
• This PR is not a code change (e.g. documentation, README, typehinting,
  examples, ...).

Checklist

• I have searched the open pull requests for duplicates.
• If code changes were made then they have been tested.
  • I have updated the documentation to reflect the changes.
• If type: ignore comments were used, a comment is also left explaining why.
• I have updated the changelog to include these changes.

[codecov]

Codecov Report

Merging #2127 (cbcadf2) into master (297053d) will decrease coverage by 0.01%.
Report is 16 commits behind head on master.
The diff coverage is 32.62%.

❗ Current head cbcadf2 differs from pull request most recent head c7741ac. Consider uploading reports for the commit c7741ac to get more accurate results

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2127      +/-   ##
==========================================
- Coverage   33.86%   33.85%   -0.01%     
==========================================
  Files         109      110       +1     
  Lines       22367    22508     +141     
==========================================
+ Hits         7575     7621      +46     
- Misses      14792    14887      +95     

Flag	Coverage Δ
macos-latest-3.10	33.83% <32.62%> (-0.01%)	⬇️
macos-latest-3.11	33.83% <32.62%> (-0.01%)	⬇️
macos-latest-3.8	33.84% <32.62%> (-0.01%)	⬇️
macos-latest-3.9	33.84% <32.62%> (-0.01%)	⬇️
ubuntu-latest-3.10	33.83% <32.62%> (-0.01%)	⬇️
ubuntu-latest-3.11	33.83% <32.62%> (-0.01%)	⬇️
ubuntu-latest-3.8	33.84% <32.62%> (-0.01%)	⬇️
ubuntu-latest-3.9	33.84% <32.62%> (-0.01%)	⬇️
windows-latest-3.10	33.83% <32.62%> (-0.01%)	⬇️
windows-latest-3.11	33.83% <32.62%> (-0.01%)	⬇️
windows-latest-3.8	33.84% <32.62%> (-0.01%)	⬇️
windows-latest-3.9	33.84% <32.62%> (-0.01%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files Changed	Coverage Δ
discord/guild.py	23.63% <18.75%> (-0.09%)	⬇️
discord/onboarding.py	27.61% <27.61%> (ø)
discord/http.py	24.35% <33.33%> (+0.06%)	⬆️
discord/enums.py	82.45% <84.61%> (+0.04%)	⬆️
discord/__init__.py	100.00% <100.00%> (ø)

---

Continue to review full report in Codecov by Sentry.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 0763261...c7741ac. Read the comment docs.

[NeloBlivion]

As far as I'm aware, this last push fully covers the onboarding features. It also includes the new convenience functions add/append_prompt, get_prompt and delete_prompt.