Add getFeedGenerators endpoint

Query feeds with a left join to users, limit results by params.size, and
present data as FeedGeneratorsView

apps/api/src/xrpc/app/rocksky/feed/getFeedGenerators.ts

···
+import { Server } from "lexicon";
+import { Context } from "context";
+import { Effect, pipe } from "effect";
+import type { FeedGeneratorsView } from "lexicon/types/app/rocksky/feed/defs";
+import type { QueryParams } from "lexicon/types/app/rocksky/feed/getFeedGenerators";
+import tables from "schema";
+import { SelectFeed } from "schema/feeds";
+import { eq } from "drizzle-orm";
+import { SelectUser } from "schema/users";
+
+export default function (server: Server, ctx: Context) {
+  const getFeedGenerators = (params) =>
+    pipe({ params, ctx }, retrieve, Effect.flatMap(presentation));
+  server.app.rocksky.feed.getFeedGenerators({
+    handler: async ({ params }) => {
+      const result = await Effect.runPromise(getFeedGenerators(params));
+      return {
+        encoding: "application/json",
+        body: result,
+      };
+    },
+  });
+}
+
+const retrieve = ({ params, ctx }: { params: QueryParams; ctx: Context }) => {
+  return Effect.tryPromise({
+    try: () =>
+      ctx.db
+        .select()
+        .from(tables.feeds)
+        .leftJoin(tables.users, eq(tables.feeds.userId, tables.users.id))
+        .limit(params.size || 100)
+        .execute(),
+    catch: (error) => Effect.fail(error),
+  });
+};
+
+const presentation = (
+  data: { users: SelectUser; feeds: SelectFeed }[],
+): Effect.Effect<FeedGeneratorsView, never> => {
+  return Effect.sync(() => ({
+    feeds: data.map(({ users, feeds }) => ({
+      id: feeds.id,
+      name: feeds.displayName,
+      description: feeds.description,
+      avatar: feeds.avatar,
+      uri: feeds.uri,
+      creator: {
+        id: users.id,
+        did: users.did,
+        handle: users.handle,
+        displayName: users.displayName,
+      },
+    })),
+  }));
+};

apps/api/src/xrpc/index.ts

···
 import spotifyPrevious from "./app/rocksky/spotify/previous";
 import spotifySeek from "./app/rocksky/spotify/seek";
 import getStats from "./app/rocksky/stats/getStats";
+import getFeedGenerators from "./app/rocksky/feed/getFeedGenerators";
 
 export default function (server: Server, ctx: Context) {
   // app.rocksky
···
   insertFiles(server, ctx);
   removePlaylist(server, ctx);
   startPlaylist(server, ctx);
+  getFeedGenerators(server, ctx);
 
   return server;
 }