We expect a string, which is parsed via `from_json`.

This matches previous usage in inventories, as well as what the
user-controlled precedessor of this variable (`matrix_synapse_admin_configuration_extension_json`)
is like.

Related to 997e6ca611

Related to https://github.com/spantaleev/matrix-docker-ansible-deploy/issues/4459

Signed-off-by: Suguru Hirahara <acioustick@noreply.codeberg.org>

This:

- brings consistency - no more mixing `_name_prefix` and `_registry_prefix`
- adds extensibility - a future patch will allow reconfiguring all registry prefixes for all roles in the playbook

We still have `_docker_` vs `_container_` inconsistencies.
These may be worked on later.

* This push request is about handling Traefik ipallowlist to synapse-admin application.

It's my first push request. If I forgot something please let me know. :-)

* Changed position of variable and naming for better expandebility of traefik options

* Remove useless `noqa var-naming` comment and too many blank lines at the end of the file

---------

Co-authored-by: AkDk7 <joerg@pannbacker.email>
Co-authored-by: Slavi Pantaleev <slavi@devture.com>

https://github.com/etkecc/synapse-admin/releases/tag/v0.10.3-etke31

* synapse-admin v0.10.3-etke15: Upgrade to react-admin v5

* v0.10.3-etke16

* fix linter

* add _auto and _custom vars

* Use 2 spaces before #noqa var-naming

---------

Co-authored-by: Slavi Pantaleev <slavi@devture.com>

* fix synapse-admin image prefix

* fix typo

* switch to synapse-admin fork

* Fix typo

* Close unclosed ) and reword sentence

---------

Co-authored-by: Slavi Pantaleev <slavi@devture.com>

As reported in https://github.com/spantaleev/matrix-docker-ansible-deploy/issues/3451#issuecomment-2331316593

Likely the solution to https://github.com/spantaleev/matrix-docker-ansible-deploy/issues/3451