Wheel problem while installing CKAN extension in docker

[iag-ggos]

I am a newbie in CKAN and just installed CKAN with the official docker compose setup. It's now successfully running. Then I tried to install and activate the extensions (ckanext-spatial). I downloaded the extensions git projects (with git clone ...) to the .../ckan-docker/src directory and inserted the plugins (spatial_metadata and spatial_query) in the .env file.

After start running the docker files with docker compose -f ~/ckan-docker/docker-compose.dev.yml up it breaks because the installation of required packages (pyproj and shapely) did not worked. I got following errors while building wheel for this package. I also tried it out by directly going into the docker container (docker exec -it ckan /bin/bash) and install these packages (pip install ...) but with the same result. I also tried to update/reinstall wheel.

So my question, why is there a problem with wheel and how can I solve this?

ckan        |   Collecting pyproj==3.4.1 (from -r /srv/app/src_extensions/ckanext-spatial/requirements.txt (line 9))
ckan        |   Using cached pyproj-3.4.1.tar.gz (217 kB)
ckan        |   Installing build dependencies: started
ckan        |   Installing build dependencies: finished with status 'done'
ckan        |   Getting requirements to build wheel: started
ckan        |   Getting requirements to build wheel: finished with status 'error'
ckan        |   error: subprocess-exited-with-error
ckan        |
ckan        |   × Getting requirements to build wheel did not run successfully.
ckan        |   │ exit code: 1
ckan        |   ╰─> [2 lines of output]
ckan        |       <string>:10: DeprecationWarning: pkg_resources is deprecated as an API. See https://setuptools.pypa.io/en/latest/pkg_resources.html
ckan        |       proj executable not found. Please set the PROJ_DIR variable. For more information see: https://pyproj4.github.io/pyproj/stable/installation.html
ckan        |       [end of output]
ckan        |
ckan        |   note: This error originates from a subprocess, and is likely not a problem with pip.
ckan        | error: subprocess-exited-with-error
ckan        |
ckan        | × Getting requirements to build wheel did not run successfully.
ckan        | │ exit code: 1
ckan        | ╰─> See above for output.
ckan        |
ckan        | note: This error originates from a subprocess, and is likely not a problem with pip.

[kowh-ai]

Is proj installed? If not, install proj like this: apk add proj-util

[iag-ggos]

Thanks. I have installed it with apk add proj-util and it worked.