Deprecate imap_content_sensor

[jbouwh]

Proposed change

Deprecate the imap_email_content_integrations. The IMAP server config can be migrated to the imap integration with a repair flow. A yaml configuration is generated to set up a template sensor and is shown in the flow to allow the user to copy and past the config into configuration.yaml.

Base on the original configuration:

sensor:
  - platform: imap_email_content
    name: Notifications
    server: imap.example.com
    port: 993
    username: user@example.com
    password: LdH0@gv!
    folder: INBOX.Notification
    value_template: "{{ subject }}"

The repair flow will look like:

The next step:

If the IMAP config is migrated but the user has not removed the imap_email_content configuration from configuration.yaml the next time Home Assistant is started, then a non fixable issue is created.
With that warning again is shown how to setup a template sensor with together with the imap config entry.

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)
• Deprecation (breaking change to happen in the future)
• Breaking change (fix/feature causing existing functionality to break)
• Code quality improvements to existing code or addition of tests

Additional information

• This PR fixes or closes issue: fixes #
• This PR is related to issue:
• Link to documentation pull request: Remove deprecated imap_content_sensor integration documentation home-assistant.io#26792

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
• I have followed the perfect PR recommendations
• 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.
• For the updated dependencies - a link to the changelog, or at minimum a diff between library versions is added to the PR description.
• Untested files have been added to .coveragerc.

To help with the load of incoming pull requests:

• I have reviewed two other open pull requests in this repository.

[home-assistant]

Please take a look at the requested changes, and use the Ready for review button when you are done, thanks 👍

Learn more about our pull request process.

[jbouwh]

@MartinHjelmare Created an import flow. If that fails the issue is replaced with a non fixable issue.
Not sure how to check if the import already was done other than calling the source import step.

TODO: Add tests for imap import flow

[MartinHjelmare]

The rest looks good!

[MartinHjelmare]

Great!

[MartinHjelmare]

Thanks!