Related to:
- https://github.com/spantaleev/matrix-docker-ansible-deploy/pull/2565
- https://github.com/spantaleev/matrix-docker-ansible-deploy/pull/2566

* added dendrite captcha options

* added hcaptcha doc

* proper url

* Apply suggestions from code review

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

* Update main.yml

* renamed captcha vars to new naming scheme

* change vars to new format

* Rename back some incorrect renamed variables

These variables are either not just part of the `client_api` subsection,
or are not even part of that section at all. They shouldn't have been
renamed in baaef2ed616e2645550d9

* Fix up naming inconsistencies

Some of these variables had been renamed in one place,
but not in other places, so it couldn't have worked that way.

* Add validation/deprecation for renamed Dendrite variables

Related to 4097898f885cf4c73, baaef2ed616e2645550, 68f4418092fa8ad
and a0b4a0ae6b2f1f18

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

* add auto join option to dendrite config

* added   auto_join_rooms: variable

* added "configuring dendrite" entry

* created dendite configuration documentation

* fixed config path

* Update docs/configuring-playbook-dendrite.md

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

* Update docs/configuring-playbook-dendrite.md

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

* Update docs/configuring-playbook-dendrite.md

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

* Update docs/configuring-playbook-dendrite.md

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

* Update docs/configuring-playbook-dendrite.md

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

* Update roles/custom/matrix-dendrite/defaults/main.yml

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

* correction

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

This paves the way for installing other roles into `roles/galaxy` using `ansible-galaxy`,
similar to how it's done in:

- https://github.com/spantaleev/gitea-docker-ansible-deploy
- https://github.com/spantaleev/nextcloud-docker-ansible-deploy

In the near future, we'll be removing a lot of the shared role code from here
and using upstream roles for it. Some of the core `matrix-*` roles have
already been extracted out into other reusable roles:

- https://github.com/devture/com.devture.ansible.role.postgres
- https://github.com/devture/com.devture.ansible.role.systemd_docker_base
- https://github.com/devture/com.devture.ansible.role.timesync
- https://github.com/devture/com.devture.ansible.role.vars_preserver
- https://github.com/devture/com.devture.ansible.role.playbook_runtime_messages
- https://github.com/devture/com.devture.ansible.role.playbook_help

We just need to migrate to those.