1454 notifications replace guest access request notification

[rekt-hard]

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Description

closes #1454
addresses sending out emails on submit: https://github.com/zenodo/rdm-project/issues/11#issuecomment-1708483567
depends on inveniosoftware/invenio-users-resources#111

Replaces EmailOp with NotficationOp. This will allow easy customization of sent notifications.
Send notification on guest access submit action.

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[rekt-hard]

General note on templates: The exact wording should be discussed and if the user info should be included as well. Something like ... was submitted by {full_name} ({email}) would be nice.