parseLoadPayload for POST request

[nycruslan]

Adding parseLoadPayload for POST request.

For everybody working with GraphQL or who would like to send a POST request - the parseLoadPayload function will be handy. It gets access to languages and namespaces and can parse the data before it has been sent by loadPath.

Checklist

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• [x] run tests npm run test
• [ ] tests are included
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Checklist (for documentation change)

• [x] only relevant documentation part is changed (make a diff before you submit the PR)
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[adrai]

Why not using the existing request option?

[nycruslan]

That's a good question.

When working with GraphQL would be convenient to have access to the namespaces and languages for generating a correct GraphQL POST request.

Here is a simple use case for this:

{
    loadPath: url.toString(),

    parseLoadPayload([locale]: string[], [ns]: string[]) {

      const {  variables } = graphqlVariables(ns);
      const query = queries[ns];

      const graphqlQuery = {
        query,
        variables: {
          locale,
          ...variables,
        },
      };

      return graphqlQuery;
    },

    parse(resp: string) {
      const { data } = JSON.parse(resp);
      return data;
    },
}

I considered updating the request function to access namespaces and languages, but it will require significant updates and may cause breaking changes. Same with parsePayload.

[nycruslan]

The request function definitely works when using additional HTTP clients like Apollo Client or Axios to make a POST request.

But since requestOptions is making a POST request, this update could be a nice addition.

[phairow]

Access to namespace and language would allow loading content using post payload rather than url path or using query parameters.

[adrai]

included in v2.2.0 thank you for your contribution