Add more information to discovery API

[frenck]

Proposed change

Add more information to the /api/discovery_info endpoint.
Mainly, external_url, internal_url and the instance UUID.

Response:

{"base_url": "http://test.local", "external_url": null, "internal_url": "http://test.local", "location_name": "Test", "requires_api_password": true, "uuid": "3ae7b1eaa31340fb8fa403de8507908f", "version": "0.111.0.dev0"}

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

Additional information

• This PR fixes or closes issue: fixes #
• This PR is related to issue:
• Link to documentation pull request:

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

[probot-home-assistant]

Hey there @home-assistant/core, mind taking a look at this pull request as its been labeled with a integration (api) you are listed as a codeowner for? Thanks!
_{^{(message by CodeOwnersMention)}}

[bdraco]

LGTM

{"base_url": "https://snip:8123", "external_url": "https://snip:8123", "internal_url": null, "location_name": "snip", "requires_api_password": true, "uuid": "snip", "version": "0.110.0.dev0"}

Tested and working as expected