fix(plugin): allow Topbar plugin to read url param on load (#8168)

* fix(plugin): allow Topbar plugin to read url param on load

* fix(plugin): add cypress tests for topbar w/o query config

test/e2e-cypress/tests/features/plugins/topbar/linking-to-configured-urls.js

@@ -0,0 +1,23 @@
+describe("Loading specs by url.primaryName param", () => {
+  describe("with no param", () => {
+    it("should load the default spec", () => {
+      cy.visit("/pages/multiple-urls/index.html")
+      .get("span.url")
+      .contains("/documents/petstore-expanded.openapi.yaml")
+    })
+  })
+  describe("with an invalid param", () => {
+    it("should fall back to the default spec", () => {
+      cy.visit("/pages/multiple-urls/index.html?urls.primaryName=undefinedUrlName")
+      .get("span.url")
+      .contains("/documents/petstore-expanded.openapi.yaml")
+    })
+  })
+  describe("with a valid url.primaryName param", () => {
+    it("should render the requested spec", () => {
+      cy.visit("/pages/multiple-urls/index.html?urls.primaryName=Petstore Swagger")
+      .get("span.url")
+      .contains("/documents/petstore.swagger.yaml")
+    })
+  })
+})