Add example of working with Git submodules

[Fredrik10a]

Applicable Issues

Fixes #259

Task from the October 2024 community meeting to capture the discussion on how a submodule setup could look like.

Description of the Change

Added a page describing how to model submodules using Eiffel events.

Alternate Designs

Not Applicable

Possible Drawbacks

Nothing that I can think of

Sign-off

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Signed-off-by:

[m-linner-ericsson]

Thank you for the contribution and glad to have you onboard!

Could I ask you fill in the PR template with some text and put your signature in the form of name and email? You don't need to be very lengthy but some explanation on what the update was. I would probably have added the following:

### Applicable Issues
Task from the [October 2024 community meeting](https://hackmd.io/e5x-6vRGSnio02m8snhn0A) to capture the discussion on how a submodule setup could look like.

### Description of the Change
Added a page describing how to model submodules using Eiffel events.


### Alternate Designs
Not Applicable

### Possible Drawbacks
Nothing  that I can think of

It could be that you only wanted to create a draft PR https://github.blog/news-insights/product-news/introducing-draft-pull-requests/ . In that case we don't require you to fill in the PR template just to get the discussion started.

If you got any question please don't hesitate to ask or reach out to me. No question is too stupid.

[m-linner-ericsson]

The test fail due to old versions used by tox, #412 will fix that.

[magnusbaeck]

LGTM, just a couple of nits and a clarification request.

[magnusbaeck]

Nit: We usually refer to the Git program as "Git" and a repository as "git", but we never use "GIT".

[magnusbaeck]

If you're going to supply an alternative text for visually impaired, please make it something better than "alt text" :-)

[magnusbaeck]

What does "SourceChange API" refer to in this case? I'm not aware of any API that returns the submodules of a given commit from a repository.

[m-linner-ericsson]

You will need to rebase your change or add the fixes we did in #412 to get the PR to pass the checks.

Adding some spelling correction suggestions and links to the event documentation.

[m-linner-ericsson]

Suggested change

	This will show you one setup for the Eiffel model on how to get around the use-case where there is a sceanrio where GIT submodules are used.
	This will show you one setup for the Eiffel model on how to get around the use-case where there is a scenario where GIT submodules are used.

[m-linner-ericsson]

Suggested change

	Important drawback from this is that it does not create a linear relationship downwards. Even though one could argue that it does, but it requires knowledge about what SCC one is suposed to query.
	Important drawback from this is that it does not create a linear relationship downwards. Even though one could argue that it does, but it requires knowledge about what SCC one is supposed to query.

[m-linner-ericsson]

Propose to add a link to the events to help the reader if they want more information.

Suggested change

Depending on the solution setup, a Service can be created to listen for SCCs (Source Change Created) that carry a specific identification tag/id for the Parent repository. Upon detecting such an SCC, the Service uses the SourceChange API to read the SHA IDs of contained submodules. It then fetches the related SCCs based on these IDs. Finally, it generates a CompositionDefined (CD) event and publishes it on the bus.

Depending on the solution setup, a Service can be created to listen for [SCC](https://github.com/eiffel-community/eiffel/blob/master/eiffel-vocabulary/EiffelSourceChangeCreatedEvent.md)s (Source Change Created) that carry a specific identification tag/id for the Parent repository. Upon detecting such an SCC, the Service uses the SourceChange API to read the SHA IDs of contained submodules. It then fetches the related SCCs based on these IDs. Finally, it generates a CompositionDefined ([CD](https://github.com/eiffel-community/eiffel/blob/master/eiffel-vocabulary/EiffelCompositionDefinedEvent.md)) event and publishes it on the bus.