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

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:

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

or 

Insert your config.php content here
Make sure to remove all sensitive content such as passwords. (e.g. database password, passwordsalt, secret, smtp password, …)

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)

Insert your Nextcloud log here

Browser log

Insert your browser log here, this could for example include:

a) The javascript console log
b) The network log 
c) ...

No files or tests are named in the issue. Start by tracing how edited-document activities are grouped and rendered into notification emails, then reproduce repeated Collabora saves. Done means repeated edits to the same file produce a concise grouped summary rather than one entry per save, with coverage for the reported behavior.