Add Direct Message support for Discord integration

[vermium]

Proposed change

Type of change

• Dependency upgrade
• Bugfix (non-breaking change which fixes an issue)
• New integration (thank you!)
• New feature (which adds functionality to an existing integration)
• Breaking change (fix/feature causing existing functionality to break)
• Code quality improvements to existing code or addition of tests

Example entry for configuration.yaml:

# Example configuration.yaml
notify:
  - platform: discord
    token: YOUR_DISCORD_BOT_TOKEN

Additional information

• This PR fixes or closes issue: fixes #
• This PR is related to issue:
• Link to documentation pull request: Add discord docs for new feature home-assistant.io#12771

Checklist

• The code change is tested and works locally.
• Local tests pass. Your PR cannot be merged unless tests pass
• There is no commented out code in this PR.
• I have followed the development checklist
• The code has been formatted using Black (black --fast homeassistant tests)
• Tests have been added to verify that the new code works.

If user exposed functionality or configuration variables are added/changed:

• Documentation added/updated for www.home-assistant.io

If the code communicates with devices, web services, or third-party tools:

• The manifest file has all fields filled out correctly.
  Updated and included derived files by running: python3 -m script.hassfest.
• New or updated dependencies have been added to requirements_all.txt.
  Updated by running python3 -m script.gen_requirements_all.
• Untested files have been added to .coveragerc.

The integration reached or maintains the following Integration Quality Scale:

• No score or internal
• 🥈 Silver
• 🥇 Gold
• 🏆 Platinum

[homeassistant]

Hi @vermium-sifell,

It seems you haven't yet signed a CLA. Please do so here.

Once you do that we will be able to review and accept this pull request.

Thanks!

[Quentame]

LGMT

[ludeeus]

The current documentation only tells the user how to get the ID of a channel, not a user.
Please add a PR to update the documentation as well.

Also it doesn't state that user ID is supported.

[vermium]

home-assistant/home-assistant.io#12770

[frenck]

How do you separate the user ID and the channel ID?
Can they collide?

[vermium]

Sorry for so much problems but here you go a good doc ig home-assistant/home-assistant.io#12771

[vermium]

How do you separate the user ID and the channel ID?
Can they collide?

I seperate them with an or function that takes them and test them as a channel / a user a id cant be a server channel and a user id at same time.