feat(graphql): add graphql request helper

[matthew-gordon]

Purpose

• this adds a convenience method to wrap next's overriden fetch and make using the contentful graphql api/surface more manageable

example usage:

// lib/contentful/client.ts

import { createFetch } from "@contentful/vercel-nextjs-toolkit/graphql";

export const { fetchGraphQL } = createFetch({
  spaceId: process.env.CONTENTFUL_SPACE_ID!,
  accessToken: process.env.CONTENTFUL_ACCESS_TOKEN!,
  previewToken: process.env.CONTENTFUL_PREVIEW_ACCESS_TOKEN!,
});

// lib/contentful/api.ts

const POST_FIELDS_FRAGMENT = `#graphql
  fragment PostFields on Post {
    __typename
    sys {
      id
    }
    title
    slug
    author {
      name
    }
    coverImage {
      url
    }
    excerpt
    content {
      json
      links {
        assets {
          block {
            sys {
              id
            }
            url
            description
          }
        }
      }
    }
  } 
`;

const GET_ALL_POSTS_QUERY = `#graphql
  query GetPostQuery($where: PostFilter, $limit: Int, $preview: Boolean) {
    postCollection(where: $where, limit: $limit, preview: $preview) {
      items {
        ...PostFields
      }
    }
  }
  ${POST_FIELDS_FRAGMENT}
`;

export async function getAllBlogs(limit = 10) {
  const res = await fetchGraphQL({
     query: GET_ALL_POSTS_QUERY,
     variables:  {
       where: { 
         slug_exists: true 
       },
       limit,
       order: "slug_DESC",
     },
     revalidate: 5,
  });
 
  return res?.data?.postCollection?.items;
}