[FEATURE] Better instructions for donors trying to log in

[wendylbolm]

Is your feature request related to a problem? Please describe.
A clear and concise description of what the problem is. Ex. I'm always frustrated when [...]
Nonprofits and donors are confused as to whether or not donors should be logging in to change their recurring donations. We should have some sort of notifications at failed log-in that lets donors know that they should look in their receipts for the donation management link instead of logging in, and probably a "lost password" message if an email isn't found that they should check their emails or contact the nonprofit for the link if they're a donor.

Describe the solution you'd like
Failed log-in attempt: A notification or pop-up directing donors to check their email or contact the organization it they can't access the modal to edit their donation
Password reset email not found: A notification or pop-up directing donors to check their email or contact the organization it they can't access the modal to edit their donation

Describe alternatives you've considered
A clear and concise description of any alternative solutions or features you've considered.
We could just put this information on the log-in page and the reset page, but it would be more noticeable as a pop-up that demanded their attention

Additional context
We routinely have donors either send emails to support or contact their orgs because they try to log in to their "donor account" but can't (because they don't have a donor account).