This addresses an issue where registering as a non-existing user fails to
register nor create an account. This is due to a check added in `824e92`
that fails if there is no User model found for the address provided.

This commit fixes a bug where Public User Registration always resulted in creating a new User. Now, if a User goes to register an Account and their email already matches a User in the system, we will register the existing User. To set the registration method, go to:
Admin Panel | Settings | Users | Registration Method

This addresses issue 4043 where the User registration form does not
validate whether or not the required fields have data. This adds checks
for data in the Email field and Name field. If there is no data it will
not let you create an account.

This commit updates a bunch of files and changes a lot of phrases. Basically it extracts "Internal error occurred" from existing phrases.
I've re-ordered the phrases so "Internal error occurred" is always at the end after the actual informative error message.

Example comparison before and after this commit:
Before: 1 Phrase: "Internal error: Unable to print to PDF"
After: 2 Phrases: "Unable to print to PDF." + "Internal error occurred"

We have existing clients who do not have an account (yet) on osTicket.  We create a ticket for them from the admin interface (creating a new guest user account) and this results in an email being sent to them with details of a job carried out.  This user can then click on the link in the notification email and view the ticket as guest - and hopefully opt to register an account.

The problem seems to be this - the user clicks on the ticket number in their notification email which lets them view the ticket as a guest - there is then a link to 'register for an account' linked to http://www.example.com/account.php?do=create - but clicking this link results in a blank page.  The PHP error is:

PHP Fatal error:  Call to a member function getField() on a non-object in /home/osticket/public_html/account.php on line 35, referer: http://www.example.com/tickets.php?id=105

This seems to be related to a bug in account.php around line 34.

    // Guest registering for an account                                                                                                      
    if ($thisclient->isGuest()) {
        foreach ($thisclient->getForms() as $f)
            if ($f->get('type') == 'U')
                $user_form = $f;
        $user_form->getField('email')->configure('disabled', true);
    }

If    $f->get('type')   is not equal to 'U' then $user_form does not get set - and therefore:
    $user_form->getField('email')->configure('disabled', true);

results in the 'call member function on a non-object error'.

I think the block should be:

    // Guest registering for an account                                                                                                      
    if ($thisclient->isGuest()) {
        foreach ($thisclient->getForms() as $f)
            if ($f->get('type') == 'U') {
                $user_form = $f;
                $user_form->getField('email')->configure('disabled', true);
            }
    }

Further - to be implicit the foreach statement should have curly braces.

    // Guest registering for an account                                                                                                      
    if ($thisclient->isGuest()) {
        foreach ($thisclient->getForms() as $f) {
            if ($f->get('type') == 'U') {
                $user_form = $f;
                $user_form->getField('email')->configure('disabled', true);
            }
        }
    }

Allow fields to be configured for view / edit / required for both agents and
end users. Fields can also be disabled now so that the field remains in the
form but is no longer displayed for new entries.

Allow tickets to be created without a subject — use the help topic full name
instead.

This adds a feature for remote authentication methods for clients, such as
LDAP, which will, after successful authentication, yield a
ClientCreateRequest rather than an AuthenticatedUser. The
ClientCreateRequest represents a successful authentication and user
information lookup for a remote client. The client is then presented with a
registration page where their information for their account in the local
system can be reviewed prior to the account creation. Once created, the
client account is confirmed without an email confirmation and is logged in
immediately without reentering a password.

Otherwise, it might be possible for a forwarded email to accidentally
contain a ticket link, with which a sinister individual might be able to use
to register for account on behalf of the original client, and, at the same
time, be able to change the user's email address to his/her own.

For client account / profile updates