activity summary must be shortened for edited documents

### Steps to reproduce 1. create a word file in nextcloud in a group folder 2. one or more coworkers edit the file during one hour using collabora 3. ### Expected behaviour the notification mail should produce a summary like "user one and user two edited the file <> multiple times between hour and hour. the reporting should probably more similar to how it is presented in the web-activity list - there I get 3 lines of activities giving a good overview what happened instead of 12 lines with a timestamp for every reported change in the mail. ### Actual behaviour currently every "save" (not sure) is reported creating a long list of changes every 3-5 minutes or so whereas the link point to the same file. I could understand if the links point to versions of the very file, but this is not the case, and not possible if versions are not manually "named". ### Server configuration NC 28.0.3 Activity 2.20

Operating system:

Web server:

Database:

PHP version:

Nextcloud version: (see Nextcloud admin page)

Where did you install Nextcloud from:

Signing status:

Login as admin user into your Nextcloud and access
http://example.com/index.php/settings/integrity/failed 
paste the results here.

List of activated apps:

If you have access to your command line run e.g.:
sudo -u www-data php occ app:list
from within your Nextcloud installation folder

Nextcloud configuration:

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sudo -u www-data php occ config:list system
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or 

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Are you using an external user-backend, if yes which one: LDAP/ActiveDirectory/Webdav/...

Client configuration

Browser:

Operating system:

Logs

Nextcloud log (data/nextcloud.log)

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Browser log

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nextcloud / activity