Fixes https://github.com/spantaleev/matrix-docker-ansible-deploy/issues/1544

see Half-Shot/matrix-hookshot#167

needed for users to put private-key.pem in

see also #1527

Fixes https://github.com/spantaleev/matrix-docker-ansible-deploy/issues/1498

Hopefully fixes https://github.com/spantaleev/matrix-docker-ansible-deploy/issues/1518

https://github.com/Half-Shot/matrix-hookshot/issues/133#issuecomment-1007541580

Discussed here: https://github.com/spantaleev/matrix-docker-ansible-deploy/issues/1510

This is the equivalent of b1b4ba501f for the matrix-dendrite role.

This brings matrix-dendrite.service in line with all the other services.

We're trying to move away from implementation-specific variables,
hoping for a clean (implementation-neutral) examples/vars.yml file.

Doing this seems more reasonable and simpler.

Also get rid of `--tags=update-user-password` in the
`matrix-dendrite` role, as what we had doesn't work.

We may be able to do it with some Ansible helper or something else.
For now, we'll omit this feature.

We also need to fix `--tags=register-user`. This tag is currently
defined in both the `matrix-synapse` and `matrix-dendrite` roles.

All the `matrix_s3_*` stuff happens in the `matrix-synapse` role.

If we are to have such S3 support for Dendrite, we should probably
extract it out of the `matrix-synapse` role (into a `matrix-s3` role or
`matrix-goofys`, etc.) and wire `matrix-dendrite` accordingly.

This may or may not be done in the future though. For now, I'm
cleaning things up in the `matrix-dendrite` role.

Seems like Dendrite encourages serving both the Client and Federation
API at the same port.

Coming from Synapse and how things are done there, we have separate
ports. Using separate ports probably makes matrix-corporal (etc.)
integration easier, so separating the APIs by default probably makes
sense.