Merge pull request #6399 from backstage/freben/fetch-api

Add `fetchApiRef` which implements fetch, plus Backstage token header when available

.changeset/blue-queens-sniff.md

@@ -0,0 +1,7 @@
+---
+'@backstage/app-defaults': patch
+'@backstage/core-app-api': patch
+'@backstage/core-plugin-api': patch
+---
+
+Add `FetchApi` and related `fetchApiRef` which implement fetch, with an added Backstage token header when available.

.changeset/itchy-grapes-think.md

@@ -0,0 +1,25 @@
+---
+'@backstage/plugin-catalog': patch
+---
+
+Deprecated the `CatalogClientWrapper` class.
+
+The default implementation of `catalogApiRef` that this plugin exposes, is now powered by the new `fetchApiRef`. The default implementation of _that_ API, in turn, has the ability to inject the user's Backstage token in requests in a similar manner to what the deprecated `CatalogClientWrapper` used to do. The latter has therefore been taken out of the default catalog API implementation.
+
+If you use a custom `fetchApiRef` implementation that does NOT issue tokens, or use a custom `catalogApiRef` implementation which does NOT use the default `fetchApiRef`, you can still for some time wrap your catalog API in this class to get back the old behavior:
+
+```ts
+// Add this to your packages/app/src/plugins.ts if you want to get back the old
+// catalog client behavior:
+createApiFactory({
+  api: catalogApiRef,
+  deps: { discoveryApi: discoveryApiRef, identityApi: identityApiRef },
+  factory: ({ discoveryApi, identityApi }) =>
+    new CatalogClientWrapper({
+      client: new CatalogClient({ discoveryApi }),
+      identityApi,
+    }),
+}),
+```
+
+But do consider migrating to making use of the `fetchApiRef` as soon as convenient, since the wrapper class will be removed in a future release.

.changeset/lovely-drinks-kiss.md

@@ -0,0 +1,5 @@
+---
+'@backstage/catalog-client': patch
+---
+
+Add the ability to supply a custom `fetchApi`. In the default frontend app setup, this will use the `fetchApiRef` implementation.