[Feature request] Make integrations such as Google Calendar, Outlook, and Apple Calendar optional

[NicoDuclos]

Make integrations such as Google Calendar, Outlook, and Apple Calendar optional.

The various integrations could be enabled or disabled in a configuration file.

For example, if the Google, Microsoft, and Apple options are all disabled, users could add their availability manually directly.

And if some integrations are disabled, only the options that are relevant to users would be offered.

[tshort]

I'd like this. For my company (and I suspect others), Outlook permissions require admin approval which will never come. That means recipients go through several clicks before finding they can't use it.