Multiproject data data source

[Simply007]

Motivation

Allow users to load data from more than one project.

Proposed solution

Extend a configuration object by the project identification property that would create the project-specific prefix for created Nodes.

Configuration example:

       {
      resolve: `gatsby-source-kentico-cloud`,
      options: {
        project1: {
          deliveryClientConfig: {
            projectId: `firstProjectGuid`,
          },
          languageCodenames: [
            `en-US`,
            `es-ES`,
          ]
        },
        project2: {
          deliveryClientConfig: {
            projectId: `secondProjectId`,
          },
          languageCodenames: [
            `en-US`,
          ]
        }
      }
    }

Possible workaround

Using Kontent Delivery API directly (or using JS SDK) without the GraphQL layer might work as a workaround:
https://www.gatsbyjs.com/docs/how-to/querying-data/using-gatsby-without-graphql/

[Simply007]

Note:

I have tested out a 🚩 really HACKY 🚩 thing with the source plugin and it is definitely not recommended to use it like that in production, but registering the plugin twice with different configurations works if the types are two distinct sets.

gatsby.config.js

[
    // ...
    {
      resolve: '@kentico/gatsby-source-kontent',
      options: {
        projectId: "FIRST_PROJECT", // Fill in your Project ID
        languageCodenames: ["default"]
      },
    },
    {
      resolve: '@kentico/gatsby-source-kontent',
      options: {
        projectId: "SECOND_PROJECT", // Fill in your Project ID
        languageCodenames: ["default"]
      },
    }
    // ...
]

The only thing is this error

A field extension with the name `kontent_item_language_link` has already been registered.

But this might be another approach to implement it - allow registering source plugin multiple times like i.e. gatsby-source-filesystem