[Feature]: Prevent removal of entries if source is corrupt

[hillbicks]

I propose a feature for:

Sources

Describe your wanted feature

Hi there,

first of all, thanks for this integration another QOL improvement.

Now, i realize this is probably not that straight forward to implement, but let me explain nonetheless.

Apparently the integration loads the ics file upon a home assistant restart. Normally the ics files contains 4 different types of waste for my street, but from time to time the file contains only one entry for the "schadstoffmobil" which is not that interesting. I double checked this one time by downloading the file from the providers website and could confirm, yes, only type in there. So it makes sense that these entries are deleted in the HA calendar as well, although not what I want obviously.

I already wrote the provider of the ics file to please fix this on their end and either make sure the file contains all entries or not upload the incomplete.

this comment confirms the current behavior:

There is currently no way to store events that are no longer provided by the source. The source probably does not get the dates anymore, and all events are erased if new ones are fetched. I can take a look if the is way to get the past dates for your source if you say which one you're using.

Maybe there is a way in the future to prevent this behavior even if the error is at the source, but some way to either get notified or prevent the deletion of entries in the future would be nice.

Thanks again