feat: Move to passport for authentication (#1934)

- Added `accountProvisioner`
- Move authentication to use passport strategies
- Make authentication more pluggable
- Change language of services -> providers

closes #1120

server/types.js

@@ -1,6 +1,6 @@
 // @flow
 import { type Context } from "koa";
-import { User } from "./models";
+import { User, Team } from "./models";
 
 export type ContextWithState = {|
   ...$Exact<Context>,
@@ -10,3 +10,13 @@ export type ContextWithState = {|
     authType: "app" | "api",
   },
 |};
+
+export type ContextWithAuthMiddleware = {|
+  ...$Exact<ContextWithState>,
+  signIn: (
+    user: User,
+    team: Team,
+    providerName: string,
+    isFirstSignin: boolean
+  ) => void,
+|};