fix: render mfe-ports for unmounted mfes when these exist

[hinakhadim]

Description

The issue occurs when all MFEs (Micro Frontends) are mounted, and the ports section in the Docker configuration is left empty, leading to a syntax error in the generated Dockerfile. Specifically, the ports: line becomes invalid as another key follows it (auth:) without any content. In the tutor dev context, the issue occurs because developers mount MFEs for testing purposes. It won't reproduce for tutor local.

...

mfe:
    ports:
auth:
   ....

How to Reproduce

• Clone all MFEs (authn, account, communications, course-authoring, discussions, gradebook, learner-dashboard, learning, ora-grading, profile)
• Run tutor mounts add $(pwd)/frontend-app-* where * represents all MFEs name one by one
• tutor config save
• tutor dev start OR directly check the mfe-ports section in tutor-env/env/dev/docker-compose.yml

What this PR does

This PR resolves the issue by implementing logic to first check if any unmounted MFEs exist. If unmounted MFEs are found, their corresponding ports are rendered in the ports: section. This ensures that the Docker configuration is generated correctly and avoids errors caused by leaving the ports: section empty.

TestCases:

• If any unmounted MFE exists, its corresponding port should be rendered under the mfe: ports: section.

...

mfe:
    ports:
        - 1997:8002 # account
        - 1984:8002 # communications

authn:
    image: ...
...           

• If no unmounted MFEs exist, the mfe: ports: section should be excluded entirely from the generated output.

...
#There should be no section of mfe->ports

authn:
     image: ....
...          

Closes #242

[regisb]

This solution is way better than the one I initially suggested. Please just add a changelog entry and add "close #242" to your commit message.

[regisb]

nit: {% if unmounted_mfes|length > 0 %}

[regisb]

Could we simplify this declaration with the following?

{%- set unmounted_mfes = [(app_name, app) for app_name, app in iter_mfes() if not list(iter_mounts(MOUNTS, app_name))] %}

[hinakhadim]

It's giving error: Error: Template syntax error: expected token ',', got 'for'. Because of , in app_name, app. I've also tried with iter_mfes().items(). Got same error.

[regisb]

Right. In which case, I suggest to expose a unmounted_mfes variable via the ENV_TEMPLATE_VARIABLES filter.

[DawoudSheraz]

shouldn't append be enough by itself? Is it necessary to set the output to _?