Add support for custom templates and extra template data

[joshbode]

• point to a directory containing template overrides
  (BaseModel.jinja2, etc)
• add custom data to templates for rendering from JSON file to support
  incorporating data that exists outside of openapi spec

[codecov]

Codecov Report

Merging #71 into master will not change coverage.
The diff coverage is 100%.

@@          Coverage Diff          @@
##           master    #71   +/-   ##
=====================================
  Coverage     100%   100%           
=====================================
  Files          12     12           
  Lines         625    644   +19     
  Branches      121    124    +3     
=====================================
+ Hits          625    644   +19

Impacted Files	Coverage Δ
datamodel_code_generator/model/pydantic/types.py	100% <100%> (ø)	⬆️
datamodel_code_generator/__main__.py	100% <100%> (ø)	⬆️
...tamodel_code_generator/model/pydantic/dataclass.py	100% <100%> (ø)	⬆️
datamodel_code_generator/model/base.py	100% <100%> (ø)	⬆️
..._code_generator/model/pydantic/custom_root_type.py	100% <100%> (ø)	⬆️
...amodel_code_generator/model/pydantic/base_model.py	100% <100%> (ø)	⬆️
datamodel_code_generator/parser/openapi.py	100% <100%> (ø)	⬆️

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[koxudaxi]

I feel good.

[koxudaxi]

Thank you very much.

[joshbode]

Awesome - thank you again for accepting

• sorry for the chain of PRs - I'm working up to something bigger (hint: it's an API client :)

[koxudaxi]

@joshbode

No problem :)

(hint: it's an API client :)

Will it be opened? (it's interesting)

I want to develop a code generator for a server of fastapi and client.
But, I'm busy with another project.

[joshbode]

yes, I hope so :)

it's for an internal project at the moment (and as such is a little idiosyncratic, hence the desire to be able to modify templates a little, and inject some extra data) but as things settle down, I'll try to roll more of my steps back into the generator :)

[koxudaxi]

If I will develop a code generator(maybe for server, client) then, I will ping you. because we should save the resource to develop :)