Less magical custom hash mechanism.

Signed-off-by: Eric Peterson <i.am@eric.pe>

plugins/analytics-module-ga/README.md

@@ -128,35 +128,32 @@ enable this...
 Note that, to comply with GA policies, the value of the User ID is
 pseudonymized before being sent to GA. By default, it is a `sha256` hash of the
 current user's `userEntityRef` as returned by the `identityApi`. To set a
-different value, provide a custom implementation of the `identityApi` that
-resolves a `userEntityRef` of the form `PrivateUser:namespace/YOUR-VALUE`. For
-example:
+different value, provide a `userIdTransform` function alongside `identityApi`
+when you instantiate `GoogleAnalytics`. This function will be passed the
+`userEntityRef` as an argument and should resolve to the value you wish to set
+as the user ID. For example:
 
 ```typescript
+import {
+  analyticsApiRef,
+  configApiRef,
+  identityApiRef,
+} from '@backstage/core-plugin-api';
+import { GoogleAnalytics } from '@backstage/plugin-analytics-module-ga';
+
 export const apis: AnyApiFactory[] = [
   createApiFactory({
     api: analyticsApiRef,
-    deps: { config: configApiRef, identityApi: identityApiRef },
-    factory: ({ identityApi, config }) => {
-      return new PseudononymizedIdentity(identityApi);
-    },
+    deps: { configApi: configApiRef, identityApi: identityApiRef },
+    factory: ({ configApi, identityApi }) =>
+      GoogleAnalytics.fromConfig(configApi, {
+        identityApi,
+        userIdTransform: async (userEntityRef: string): Promise<string> => {
+          return customHashingFunction(userEntityRef);
+        },
+      }),
   }),
 ];
-
-class PseudononymizedIdentity implements IdentityApi {
-  constructor(private actualApi: IdentityApi) {}
-  async getBackstageIdentity(): Promise<BackstageUserIdentity> {
-    const { email = 'someone' } = await this.actualApi.getProfileInfo();
-    const hashedEmail = customHashingFunction(email);
-
-    return {
-      type: 'user',
-      userEntityRef: `PrivateUser:default/${hashedEmail}`,
-      ownershipEntityRefs: [],
-    };
-  }
-  // ...
-}
 ```
 
 ### Debugging and Testing