Bug 36505: Add support for `extended_attributes` in PUT /patrons/:patron_id

Bug 36505: Add support for `extended_attributes` in PUT /patrons/:patron_id

This patch does what the title says. With it, you will be able to PUT on
the already existing endpoint, but also pass:

```json
[ { "type": "THE_TYPE", "value": "a" }, ... ]
```

Bonus: to ease testing I added `x-koha-embed: extended_attributes`
support.

To test:
1. Apply the unit tests
2. Run:
   $ ktd --shell
  k$ prove t/db_dependent/api/v1/patrons.t
=> FAIL: This is not implemented!
3. Apply this patch
4. Repeat 2
=> SUCCESS: Exhaustive testes pass!
5. Sign off :-D

Signed-off-by: Brendan Lawlor <blawlor@clamsnet.org>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Katrin Fischer <katrin.fischer@bsz-bw.de>