07fec4c4 introduced the ability to receive
and process messages forwarded as a message/rfc822. However, the email
headers that were saved on file in the %email_info_table were the headers of
the outer message.

This patch pulls the headers from the wrapped message to be saved in the
database. This mainly addresses the email References and In-Reply-To headers
for the email responses from the system.

Some emails providers (e.g gmail/google) won't deliver emails marked
bulk/autoreply to group email address.

This is required when validating a message which could be a string or an
object.

level.
Handle cases where thready body is sent in as a string

We're going to assume HTML of html thread is enabled - otherwise text is
assumed.

model.

This would in theory allow us to decide at the email level the content type
to accept.

Cleanup and make HTML safe by default
Strip empty lines in TEXT content

This will be helpful to keep track of whether a text is html or text and
provide a way to convert it exactly once.

Until we add text/plain bodies to the ticket thread without an enclosing
<pre> element, we should not treat the <pre> element like a code or
blockquote block.

On some combinations of operating systems, PHP and libpcre versions, `\s`
will match the iso-8859-x non-breaking-space, 0xa0. This regular expression
will munge the UTF8 encoded version, 0xc2a0 to 0xc220, which is not a valid
UTF8 character.

When inserted into a UTF8 field in mysql, the text will be truncated at and
after the first invalid character.

These functions don't appear to be used an could corrupt UTF-8 encoded text

Fixes a few E_NOTICE messages
Drops bounce checking inside autoReply checking

If MySQL error #1213 (deadlock found when trying to get lock) is returned
from query, it is safe to retry the query.

This patch will retry queries up to two times for a total of three. If the
query cannot be executed without error #1213 after the third time, the error
is logged as usual, and the system continues with the failed query.

If a file is attached via email and sent into the system, and a file is on
record with the same signature (hash) and size, the system will not save the
file. Instead, the key of the existing file would be found and used instead.

This patch fixes a bug in AttachmentFile::save. The key was generated for
the new file; however, if it was determined to be a duplicate, the key of
the existing file was not returned. Therefore generated key, which wasn't
saved to the database, was returned. Therefore, the wrong key was placed in
the body of the message with cid:<key> for inline images, although that key
would not exist in the database.

This patch correctly returns the existing key from the ::save() method
for de-duplicated files.

Rename routines to make it a little clear on what they do

This patch addresses an issue where a client may have upper-case letters in
their email address. When visiting the client portal to check the ticket
status, previously, the exact same case would be required in the 'Email
Address' box.

This patch removes the case sensitivity for email logins.

If the content of the message is of type `message/rfc822`, then support
downloading the body of the message and sending it off to the mail parsing
system, simulating a piped email.

They are only available for tickets arriving via the email channel. All
other channel (including email) use the new ticket form to record the
subject and body, which are mapped to the 'Issue Summary' and 'Issue
Details' fields respectively

Structure the drop-down list for the `what` column to be future-minded
concerning custom user data matching.

Previously, if a message had a Content-Disposition header, then it could not
be considered as the body of the message.

If the mail received into the system has a content type of 'message/rfc822',
then unwrap the inner message and use it as the parsed email. Effectively,
assume the email was forwarded as an message/rfc822 attachment.

Previously, the subject was duplicated, which is really confusing

This patch partially reverts the previous database migration patch which
added a primary key to the table on the `thread_id` column. This column
cannot be used, because there may be multiple entries for thread_id = 0.

This also allows ticket_collaborator.isactive to be negative, as well as
adds the database portion of regex support for ticket filters.

Exclude the auto-responding email from possible alerts sent to staff

The concern here is possible loop when an alert to staff bounces back to the
system.

Disable auto-response on a bounce.