feat(adapters): let user configure MongoDB database name (#5290)

* feat: added providing database name in options

* fix: added database name providing in readme

* Apply suggestions from code review

Co-authored-by: Balázs Orbán <info@balazsorban.com>

packages/adapter-mongodb/README.md

@@ -72,7 +72,9 @@ import clientPromise from "lib/mongodb"
 // For more information on each option (and a full list of options) go to
 // https://next-auth.js.org/configuration/options
 export default NextAuth({
-  adapter: MongoDBAdapter(clientPromise),
+  adapter: MongoDBAdapter(clientPromise, {
+    databaseName: 'my-data-base-name'
+  }),
   ...
 })
 ```

packages/adapter-mongodb/src/index.ts

@@ -17,6 +17,7 @@ export interface MongoDBAdapterOptions {
     Sessions?: string
     VerificationTokens?: string
   }
+  databaseName?: string
 }
 
 export const defaultCollections: Required<
@@ -73,7 +74,7 @@ export function MongoDBAdapter(
   const { from, to } = format
 
   const db = (async () => {
-    const _db = (await client).db()
+    const _db = (await client).db(options.databaseName)
     const c = { ...defaultCollections, ...collections }
     return {
       U: _db.collection<AdapterUser>(c.Users),