Removed datamodel-code-generator from dev requirements

[ricardogsilva]

This PR removes datamodel-code-generator from dev requirements, following the discussion from #1367

Related Issue / Discussion

• removal of dependency datamodel-code-generator #1367

Contributions and Licensing

(as per https://github.com/geopython/pygeoapi/blob/master/CONTRIBUTING.md#contributions-and-licensing)

• I'd like to contribute [feature X|bugfix Y|docs|something else] to pygeoapi. I confirm that my contributions to pygeoapi will be compatible with the pygeoapi license guidelines at the time of contribution.
• I have already previously agreed to the pygeoapi Contributions and Licensing Guidelines

[ricardogsilva]

@francbartoli

[francbartoli]

Why are we removing this entire section? Maybe it's better for DX to remove only Model generation and How to merge and add a paragraph How to hack the models, what do you think?

[ricardogsilva]

What do you envision as being the content of this alternative How to hack the models section?

In my opinion it would likely make sense if you'd still like to recommend a workflow like the autogeneration of models using datamodel-code-generator and then some manual tweaking. But I don't see much value in it, as the models already exist and have modifications, so it seems more likely that further changes will not restart from scratch - in which case, it seems to me that How to hack the models is not so different from how to develop pygeoapi as a whole.

But maybe I'm missing the point 😅 ?

[ricardogsilva]

@francbartoli can I ask for more clarification on what would be the way to move this forward? I'm not really sure what I would replace the deleted docs content with.

On the other hand I'd like to move on with the work needed for #1360 and this PR is a blocker for that

[francbartoli]

@ricardogsilva I would consider relevant to keep where this model applies and it is limited to only CQL-JSON schema for the ES provider.