Creating environments using Guix package manager

[Zelphir Kaltstahl]

Hi Guix Users!

For some time now I would like to create Guix environments for separate
projects.

I've tried finding the way to do it at
https://guix.gnu.org/manual/en/html_node/Invoking-guix-environment.html
but have been unable to read out of it, how to do it.

I would like environments that have the following:

+ persistent (something with the --root argument?)
+ activate-able / deactivate-able (something like Python's environments:
source env_name/bin/activate)
+ their own dependencies, not mixed with anything in my base guix profile
+ Not only temporary
+ one time install (do not want to reinstall all packages every time I
want to use the environment)
+ simply use the environment to run programs in the environment

Today I had a conflict of versions of packages, which brought up this
issue again for me:

~~~~
building /gnu/store/yniz1rh5cih92i72flj1x2cmlwv1nngk-keepassxc-2.5.4.drv...
guix package: error: profile contains conflicting entries for gmp
guix package: error:   first entry: gmp@6.2.0 
/gnu/store/35afkywncrr5xsb4cxcljf6rpjcb7f61-gmp-6.2.0
guix package: error:    ... propagated from guile@3.0.2
guix package: error:   second entry: gmp@6.1.2 
/gnu/store/y7qk8raalgvdnxcglvxa320cfxrjk1x6-gmp-6.1.2
guix package: error:    ... propagated from nettle@3.5.1
guix package: error:    ... propagated from gnutls@3.6.A
hint: Try upgrading both `guile' and `gnutls', or remove one of them from the 
profile.
~~~~

So I cannot complete `guix package -u`. I guess some of those packages
in my base profile are not even needed for most things I do and would be
better contained in project-specific environments, so that they do not
cause conflicts.

Is it possible to create such kind of environments using Guix? I feel
like it should probably be an easy thing to do, once I know how to do
it, but I could not find a tutorial, which tells me how to do this.
Perhaps my idea about how Guix is used usually is wrong?

Regards,
Zelphir