Add config flow base strings

[balloob]

Breaking change

Proposed change

Adds common config flow strings.

• Add common strings
• Update scaffolding to use references
• Copy existing translations to placeholders. Script done, not executed.
• Go through existing strings.json and use references For follow-up PR
• Add hassfest check to find strings that can use references For follow-up PR

Testing to do:

• Validate translations for config flow template
• Validate translations for discovery config flow template
• Validate translations for oauth2 config flow template

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

[ctalkington]

just wonder would api_key be a common data string as well?

[balloob]

Yeah, and access token. Really anything that would ever be shared by more than 1 integration should be added.

[balloob]

What's happening here is that we one-time rename these keys to the common keys. Then when strings are uploaded after merge, the old names are created again, but their new value is set up as a reference to the new name.

[balloob]

So this script needs to run before merge.

[MartinHjelmare]

Merge of this PR?

[balloob]

Yes, I will do that once CI passses.