[typescript-fetch] Add option to generate validation attributes of model properties

[matthiasschwarz]

Adds a new option to generate validation attributes of model properties. This allows the use of these attributes for schema validation.

The following attributes are exposed via a lookup table of the model property:

• maxLength
• minLength
• pattern
• maximum
• exclusiveMaximum
• minimum
• exclusiveMinimum
• multipleOf
• maxItems
• minItems
• uniqueItems

The following attributes are exposed via an object when model has additional properties:

• maxProperties
• minProperties

cc @TiFu (2017/07) @taxpon (2017/07) @sebastianhaas (2017/07) @kenisteward (2017/07) @Vrolijkx (2017/09) @macjohnny (2018/01) @topce (2018/10) @akehir (2019/07) @petejohansonxo (2019/11) @amakhrov (2020/02) @davidgamero (2022/03) @mkusaka (2022/04)

PR checklist

• Read the contribution guidelines.
• Pull Request title clearly describes the work in the pull request and Pull Request description provides details about how to validate the work. Missing information here may result in delayed response from the community.
• Run the following to build the project and update samples:

  ./mvnw clean package 
  ./bin/generate-samples.sh ./bin/configs/*.yaml
  ./bin/utils/export_docs_generators.sh
  

  (For Windows users, please run the script in Git BASH)
  Commit all changed files.
  This is important, as CI jobs will verify all generator outputs of your HEAD commit as it would merge with master.
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[macjohnny]

thanks for your contribution, looks good!
can you please change the template according to my comment and then we can merge this?

[macjohnny]

Suggested change

	}{{#validationAttributes}}
	}
	{{#validationAttributes}}

[macjohnny]

you can put the stuff on new lines, like

{{#maxLength}}maxLength: {{maxLength}},{{/maxLength}}
{{#minLength}}minLength: {{minLength}},{{/minLength}}
...

this makes the template nicer to read

[matthiasschwarz]

@macjohnny I changed the formatting of the template.