[Feat]: Adding more preevy environment variables

Nobody has claimed this yet.

### What feature?

Hi,
We're setting up preevy and we've run into some minor annoyances.

From what I understand, the only preevy-related environment variable we can use is `PREEVY_BASE_URI_{SERVICE}`, however this is not sufficient for our needs for multiple reasons;

* Our application (PHP) needs to know the domain it is running on. _Just_ the domain so now we would have to do some parsing in the application to get that.
* We use minio as an S3 development alternative, and for that we need the url to the service. However the one in the preevy environment variable is http instead of https, and it has a trailing slash, which we don't need.

### Describe the solution you'd like

All our cases would be solved if we could get more preevy environment variables, like:

* the environment id (with this we could build the url ourselves)
* _just_ the host name, without the scheme and no trailing slashes

### Describe alternatives you've considered

_No response_

### Additional context

_No response_

### Add screenshots

_No response_

### Record

- [X] I agree to follow this project's Code of Conduct