Fix Office 365 calendars to be compatible with rfc5545

[allenporter]

Proposed change

Add a small module to replace invalid Office 365 TZID values with something that is valid rfc5545 content and will be parsable by the underlying library. This moves the calendar parsing code to a module shared by config flow and coordinator and uses an integration specific exception rather than the exceptions in the underlying library to prepare for adding more validations/error checking.

Context: RFC5545 requires a calendar to be fully specified. Any TZID must be referenced in VTIMEZONE. This will remove the invalid timezone and force the date entry to be in the local time (given the behavior is undefined this seems most reasonable).

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)
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• 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 Remote Calendar cannot parse Office365 calendar with invalid timezones #142164
• This PR is related to issue:
• Link to documentation pull request:
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• Link to frontend pull request:

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[home-assistant]

Hey there @Thomas55555, mind taking a look at this pull request as it has been labeled with an integration (remote_calendar) you are listed as a code owner for? Thanks!

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[allenporter]

I'm going to go with a different approach based on a new ical version. Will mark ready after the fix is in.

[allenporter]

OK, I updated this to enable a compatibility layer in ical.

[edenhaus]

Thanks @allenporter 👍