feat: upd batch enrollment email msg

[rayzhou-bit]

Description

When course authors perform batch enrollment via the instructor dashboard, they are given the message that enrollment email has successfully went out when that isn't the case. When an account has not had their email verified, batch enrollment cannot be performed. This is documented in the following places:

• [BB-1504] Fix the automatic enrollment issue for inactive user #21594
• https://2u-internal.atlassian.net/wiki/spaces/ENGAGE/pages/12025987/Account+Activation#Account-activation-for-enrollment

This PR will change the message from Successfully sent enrollment emails to the following users. They will be allowed to enroll once they register: to Email cannot be sent to the following users via batch enrollment. They will be allowed to enroll once they register:.

---

For reference, here were the messages we sent out when 'Notify users by email' are checked:
If user is enrolled:
Successfully enrolled and sent email to the following users:

If user is not enrolled and 'Auto enroll' is checked:
Successfully sent enrollment emails to the following users. They will be enrolled once they register: (will be changed by this PR)

If user is not enrolled and 'Auto enroll' is not checked, but allowed is true:
Successfully sent enrollment emails to the following users. They will be allowed to enroll once they register: (will be changed by this PR)

Testing instructions

In the instructor dashboard, enter a list of accounts with some emails that have not been verified. You should see the new message.

Other information

Ticket: https://2u-internal.atlassian.net/browse/TNL-10820

[cablaa77]

the message text looks good to me

[connorhaugh]

LGTM

[edx-pipeline-bot]

2U Release Notice: This PR has been deployed to the edX staging environment in preparation for a release to production.

[edx-pipeline-bot]

2U Release Notice: This PR has been deployed to the edX production environment.

[edx-pipeline-bot]

2U Release Notice: This PR has been deployed to the edX staging environment in preparation for a release to production.

[edx-pipeline-bot]

2U Release Notice: This PR has been deployed to the edX production environment.

[edx-pipeline-bot]

2U Release Notice: This PR has been deployed to the edX production environment.

[fghaas]

We just came across this after upgrading our platform to Quince. Can I suggest that this patch be reverted? The error message contradicts what is actually happening.

When an instructor (or the bulk enrollment API) adds a learner email address to a course that does not belong to a registered user, then that learner receives an email inviting them to register on the platform, and once they complete their registration, they are automatically enrolled in the course they have been invited to. This behavior has not recently changed, as far as I am aware.

"Email cannot be sent to the following users via batch enrollment" clearly says that those users did not receive an email message, but that is not true: they do. It is not an enrollment message, strictly speaking, but an invitation to register, but an email does go out and thus "email cannot be sent" is not the right message to display here.