This feature addresses a major issue with the initial implementation of the
custom data system. The original system confused the usage of
database-backed field (dynamic-fields) and their corresponding
implementation. This created the need to crate awkward caching pieces to
ensure that validation errors and data was maintained. Furthermore, the
system confused the linking between form instances (dynamic-entry) and the
form used to represent that entry.

This patch addresses the confusion in two ways:

Dynamic form entries do not link directly to the dynamic form. Instead, the
::getForm() method returns something from the forms API directly.
Furthermore, the ::getFields() method does not return dynamic field
instances (database backed / designed fields). Instead, the actual
implementation of the fields from the forms API is retrieved. This allows
the fields to *always* be cached, which helps preserve data and validation
state.

Secondly, the dynamic form uses the same system, so that requests to turn a
dynamic form into a form (via ::getForm) will also result in the same
behavior, again, where the fields are represented as forms API fields rather
than the dynamic fields.

So going forward, the dynamic fields are *only* used to create corresponding
forms API field implementations. The are associated with the dynamic
counterparts as sparingly as possible.

When associating objects via the ::set() method or by adding them to an
InstrumentedList, avoid saving the object immediately. Instead, lazily
update the primary and foreign key of the associated objects.

This patch adds an error to the page if unable to configure the archive
folder and POP was selected as the mailbox protocol. Generally, POP servers
do not support anything but the INBOX

Unassign tickets on transfer when the target department has assignment
restriction and the assigned staff is not a member.

Disable claim (quick self-assignment) when above restriction is in effect.

Here's an example email structure:
```
multipart/mixed
 - multipart/report; delivery-status
   - multipart/alternative
     - text/plain
     - text/html
   - message/delivery-status
   - message/rfc822
```

The previous code would only find the body if the email main headers had:
Content-Type: multipart/report; report-type="delivery-status". In such a
case it would scan for a plain/text body.

This patch will scan for the usual body if the scan for the body as usual if
the report scan did not find anything.

Also, output errors to stderr when running API from the command line

List item are only unique within the list.

It seems that most systems handle the newline character alone without a
problem; however, some systems cannot handle the standard CRLF line ending
at all.

The %ticket_email_info table needs an index on thread_id. This is done in
the `develop-next` branch; however, this patch helps alleviate performance
issues on the main branch until the `develop-next` branch is collapsed for
main line development.

Fixed typo

Support filtering search results by uid.

This also adjusts the logic internally to lookup the priority by the
priority_urgency field, which should be constrained to follow priority
precedence over the priority_id field.

Because CSV has no way of indicating a content character set, writing the
file with a Unicode byte-order mark is useful to declare the content in
UTF-8 encoding.