[Typescript-fetch] Add isBoolean blocks to modelOneOf.mustache

[elliottkember]

Adds booleans to modelOneOf

We have a union type that unions with boolean:

export type AdminSettingsModelValue = boolean | number | object | string;

This is being compiled without the boolean typeof check:

export function AdminSettingsModelValueFromJSONTyped(
  json: any,
  ignoreDiscriminator: boolean
): AdminSettingsModelValue {
  if (json == null) {
    return json;
  }
  if (typeof json === 'number') {
    return json;
  }
  if (typeof json === 'string') {
    return json;
  }
  return {} as any;
}

This PR adds the boolean sections to the template. This compiles correctly for us, and adds the boolean type to the exported union.

Any suggestions are very welcome!

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[elliottkember]

@joscha Tagging you as a listed Typescript maintainer for visibility as requested!

[wing328]

thanks for the PR

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) @joscha (2024/10)