Adds a way to get the perspective by using a shared URL

src/Ad4mClient.test.ts

@@ -320,6 +320,14 @@ describe('Ad4mClient', () => {
             expect(p.name).toBe('test-perspective-1')
         })
 
+        it('fromUrl() smoke test', async () => {
+            const p1 = await ad4mClient.perspective.fromUrl('neighbourhood://Qm12345')
+            expect(p1.sharedUrl).toBe('neighbourhood://Qm12345')
+            expect(p1.name).toBe('test-perspective-2')
+            const p2 = await ad4mClient.perspective.fromUrl('neighbourhood://Qm67891')
+            expect(p2).toBeNull()
+        })
+
         it('snapshotByUUID() smoke test', async () => {
             const ps = await ad4mClient.perspective.snapshotByUUID('00004')
             expect(ps.links.length).toBe(1)

src/perspectives/PerspectiveClient.ts

@@ -111,6 +111,19 @@ export default class PerspectiveClient {
         return new PerspectiveProxy(perspective, this)
     }
 
+    async fromUrl(url: string): Promise<PerspectiveProxy|null> {
+        const { fromUrl } = unwrapApolloResult(await this.#apolloClient.query({
+            query: gql`query fromUrl($url: String!) {
+                fromUrl(url: $url) {
+                    ${PERSPECTIVE_HANDLE_FIELDS}
+                }
+            }`,
+            variables: { url }
+        }))
+        if(!fromUrl) return null
+        return new PerspectiveProxy(fromUrl, this)
+    }
+
     async snapshotByUUID(uuid: string): Promise<Perspective|null> {
         const { perspectiveSnapshot } = unwrapApolloResult(await this.#apolloClient.query({
             query: gql`query perspectiveSnapshot($uuid: String!) {

src/perspectives/PerspectiveResolver.ts

@@ -44,6 +44,17 @@ export default class PerspectiveResolver {
         return new PerspectiveHandle(uuid, 'test-perspective-1')
     }
 
+    @Query(returns => PerspectiveHandle, {nullable: true})
+    fromUrl(@Arg('url') url: string): PerspectiveHandle|null {
+        if (url === 'neighbourhood://Qm12345') {
+            const perspective = new PerspectiveHandle(url, 'test-perspective-2');
+            perspective.sharedUrl = "neighbourhood://Qm12345";
+            return perspective;
+        }
+
+        return null;
+    }
+
     @Query(returns => Perspective, {nullable: true})
     perspectiveSnapshot(@Arg('uuid') uuid: string): Perspective|null {
         return new Perspective([testLink])