Fixes a bug related to filters appended onto next links for gatsby-source-drupal. (#31350)

Author: smurrayatwork

packages/gatsby-source-drupal/src/gatsby-node.js

@@ -249,7 +249,17 @@ exports.sourceNodes = async (
             // See https://www.drupal.org/docs/8/modules/jsonapi/filtering
             if (typeof filters === `object`) {
               if (filters.hasOwnProperty(type)) {
-                url = url + `?${filters[type]}`
+                url = new URL(url)
+                const filterParams = new URLSearchParams(filters[type])
+                const filterKeys = Array.from(filterParams.keys())
+                filterKeys.forEach(filterKey => {
+                  // Only add filter params to url if it has not already been
+                  // added.
+                  if (!url.searchParams.has(filterKey)) {
+                    url.searchParams.set(filterKey, filterParams.get(filterKey))
+                  }
+                })
+                url = url.toString()
               }
             }
           }