feat(providers): add Freshbooks (#2322)

Contains the following squashed commits: 

* Create freshbooks.js
* Create freshbooks.md
* Update providers.d.ts
* Update freshbooks.md
* Update src/providers/freshbooks.js
* Update providers.test.ts
* Update freshbooks.md

Author: Ben Goshow

src/providers/freshbooks.js

@@ -0,0 +1,20 @@
+export default function Freshbooks(options) {
+  return {
+  id: 'freshbooks',
+  name: 'Freshbooks',
+  type: 'oauth',
+  version: '2.0',
+  params: { grant_type: 'authorization_code' },
+  accessTokenUrl: 'https://api.freshbooks.com/auth/oauth/token',
+  authorizationUrl: 'https://auth.freshbooks.com/service/auth/oauth/authorize?response_type=code',
+  profileUrl: 'https://api.freshbooks.com/auth/api/v1/users/me',
+  async profile(profile) {
+    return {
+      id: profile.response.id,
+      name: `${profile.response.first_name} ${profile.response.last_name}`,
+      email: profile.response.email,
+    };
+  },
+  ...options
+  };
+}

types/providers.d.ts

@@ -72,6 +72,7 @@ export type OAuthProviderType =
   | "FACEIT"
   | "FortyTwo"
   | "Foursquare"
+  | "Freshbooks"
   | "FusionAuth"
   | "GitHub"
   | "GitLab"

types/tests/providers.test.ts

@@ -257,3 +257,9 @@ Providers.Zoho({
   clientId: "foo123",
   clientSecret: "bar123",
 })
+
+// $ExpectType OAuthConfig<Profile>
+Providers.Freshbooks({
+  clientId: "foo123",
+  clientSecret: "bar123",
+})

www/docs/providers/freshbooks.md

@@ -0,0 +1,33 @@
+---
+id: freshbooks
+title: Freshbooks
+---
+
+## Documentation
+
+https://www.freshbooks.com/api/authenticating-with-oauth-2-0-on-the-new-freshbooks-api
+
+## Configuration
+
+https://my.freshbooks.com/#/developer
+
+## Options
+
+The Freshbooks Provider comes with a set of default options:
+
+https://www.freshbooks.com/api/start
+
+You can override any of the options to suit your own use case.
+## Example
+
+```js
+import Providers from `next-auth/providers`
+...
+providers: [
+  Providers.Freshbooks({
+    clientId: process.env.FRESHBOOKS_CLIENT_ID,
+    clientSecret: process.env.FRESHBOOKS_CLIENT_SECRET,
+  })
+]
+...
+```