[geeklog-devel] Request to add a new PLG hook - add createUserPrecheck

[Blaine Lang]

While working on two projects this month, I have seen the need to have 
more control over the create new user flow.

A plugin can use the PLG_createUser hook but this is called after GL 
already adds the user. If a plugin determines that it's not safe to add 
the user for whatever reason, there is no way to effect the code flow 
that has already added the new GL users records.

We have a CUSTOM_userCheck that does something similar but thats only 
for custom registration.

A plugin may need to check that other data in the add user form is 
unique and return an error that can be displayed just like is now for 
duplicate email or member name.

If there are no objections, then I will make it so.

- Blaine