Bug 32548: Make illrequestattributes available in ILL emails

Bug 32548: Make illrequestattributes available in ILL emails

Without this ILL module only provides very limited data to
be included in the notices sent about the request itself.

We have the columns illrequests, but not the illrequestattributes,
that often will contain the more useful information needed.

This patch enables to use values of the illrequestattributs using
[% illrequestattributes.<attributname> %] in the notices.

To test:
* Apply patch
* First you'll need to activate the ILL module and install a
  backend to use it with. FreeForm was used for this test plan,
  BLDSS is usually also good for testing.
  See: https://wiki.koha-community.org/wiki/ILL_backends
* Also set up an SMTP server to use for notices and make
  sure the email address is set in KohaAdminEmailAddress
  and the user you are using for testing this with.
* Make sure your user has an email address and will receive
  ILL notices by seleting them in the messaging preferences.
* Create an ILL request with the FreeForm backend for your user.
* On the ILL request detail page: "Display supplier metadata"
  Pick some attributes you want to use in the notice
* Go to Tools > Notices and slips and edit ILL_REQUEST_UNAVAIL
* Add some of the attributes you picked. Example:
  [% illrequestattributes.type %]
  [% illrequestattributes.title %]
* Back to the ILL request detail page: Send notice to patron >
  ILL request unavailable
* Go to your patron's account and check the notices tab
* The generated notice shoudl show and include the information
  from the illrequestattributes you picked.

Signed-off-by: Pedro Amorim <pedro.amorim@ptfs-europe.com>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>