Don't validate that adhoc emails have access to view content

Problem/Motivation

Emails to addresses listed under adhoc emails are only sent if the module can verify a user account with that email has access to view the entity OR if anonymous users have access to view the content.

I find this behavior unexpected. For adhoc emails, I don't think there should be an expectation that the module does this user account lookup and access check process.

This feature was implemented in ✨ Send notifications only to users who can view content Fixed #9 and a comment from there expressed the same. I also was previously very confused by this and created 📌 Update notification form to indicate users being emailed must have access to view the content Active to at least improve the inline documentation to help avoid pitfalls.

Steps to reproduce

Proposed resolution

Let's either remove the validation for adhoc emails entirely (preferable), OR make validation configurable.

Remaining tasks

User interface changes

API changes

Data model changes