Allow filtering by contact provider.

[RokeJulianLockhart]

Checklist

• I made sure that there are no existing issues - open or closed - to which I could contribute my information.
• I made sure that there are no existing discussions - open or closed - to which I could contribute my information.
• I have read the FAQs inside the app (Menu -> About -> FAQs) and my problem isn't listed.
• I have taken the time to fill in all the required details. I understand that the bug report will be dismissed otherwise.
• This issue contains only one feature request.
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Feature description

On https://www.apkmirror.com/apk/google-inc/google-contacts/google-contacts-4-25-22-605409159-release/, https://support.google.com/docs/answer/2405894?hl=en&co=GENIE.Platform%3DAndroid&oco=0 is augmented with a list of https://developer.android.com/guide/topics/providers/contacts-provider#Sources to filter between.

Why do you want this feature?

This is useful because I usually solely want to see my NextCloud contacts, but can switch to see all of my device-synchronized or merely Google contacts easily.

Additional information

No response

[Aga-C]

There's already filtering in the app (second icon on the top). Isn't it enough?

[RokeJulianLockhart]

#84 (comment)

@Aga-C, I somehow missed that... It's actually rather more powerful due to the checkboxes allowing combinations. Thanks.