Log email sends to the relevant entity

@rszrama I've made changes in variable, methods names.
I've used condition to check if there are log templates categories for the target entity type ID to show the checkbox.
I've added description for the checkbox field.
We can add some validation message for the email edit form that the log templates are not found.
And we can add some watchdog log if the template is not created when we try to log the email.
What do you think?

I've added validation mentioned in my previous comment

Commerce already logs order related emails, is the code not generic enough to support Commerce emails?

So the reason why Commerce core doesn't log the emails sent by Commerce Email atm is because it doens't have $params['order'] set. See https://git.drupalcode.org/project/commerce/-/blame/8.x-2.x/modules/log/....

But we probably want to log the emails ourselves I suppose. Maybe we can add a flag to the params array that Commerce looks for to indicate that logging should be skipped (if not enabled).

This looks good to me! I've made some interface text adjustments prior to committing this (which bled over a little into moving both the queueing and logging checkboxes lower down the configuration form), but I appreciate the validation added. I think we'll just need to add documentation for how to define log templates outside of this module vs. try to use error messages and form help text to explain it all.

Committing!

Automatically closed - issue fixed for 2 weeks with no activity.

I think we should have made the commerce_log integration optional... Right now it is required which isn't good as people that don't really want/need the log module shouldn't have to enable it just to use commerce_email...
As soon as commerce_log is turned off, it's going to log add to cart / cart removal events etc.