This PR replaces the error string "Could not find registration details" with the LtiMessageLaunch::getMissingRegistrationErrorMsg() function. This was meant to be implemented in #63, but I missed it due to the two original error strings being different.
Testing
I copy+pasted the code in my local BE, forced the exception to always be thrown, and verified that the message appears when attempting to log in via an LTI 1.3 launch.
Screenshot
![Screenshot from 2022-07-28 13-12-24](https://user-images.githubusercontent.com/29388364/181608200-b443f5e5-7556-432f-83e8-7bf0bc88a0fd.png)
Summary of Changes
This PR replaces the error string "Could not find registration details" with the
LtiMessageLaunch::getMissingRegistrationErrorMsg()
function. This was meant to be implemented in #63, but I missed it due to the two original error strings being different.Testing
I copy+pasted the code in my local BE, forced the exception to always be thrown, and verified that the message appears when attempting to log in via an LTI 1.3 launch.
Screenshot
![Screenshot from 2022-07-28 13-12-24](https://user-images.githubusercontent.com/29388364/181608200-b443f5e5-7556-432f-83e8-7bf0bc88a0fd.png)