refactor: removed a bunch of proxied methods from provider to app

BREAKING CHANGE: The following Provider instance getters/setters are
removed: subdomainOffset, proxyIpHeader, maxIpsCount, keys. You can
access the underlying Koa app via `provider.app` if you have the need
to use these.

lib/provider.js

@@ -243,6 +243,16 @@ class Provider extends events.EventEmitter {
     return this.app.listen(...args);
   }
 
+  /* istanbul ignore next */
+  get proxy() {
+    return this.app.proxy;
+  }
+
+  /* istanbul ignore next */
+  set proxy(value) {
+    this.app.proxy = value;
+  }
+
   get Claims() { return instance(this).Claims; }
 
   get BaseToken() { return instance(this).BaseToken; }
@@ -278,16 +288,4 @@ class Provider extends events.EventEmitter {
   get requestUriCache() { return instance(this).requestUriCache; }
 }
 
-/* istanbul ignore next */
-['env', 'proxy', 'subdomainOffset', 'keys', 'proxyIpHeader', 'maxIpsCount'].forEach((method) => {
-  Object.defineProperty(Provider.prototype, method, {
-    get() {
-      return this.app[method];
-    },
-    set(value) {
-      this.app[method] = value;
-    },
-  });
-});
-
 module.exports = Provider;

types/index.d.ts

@@ -1119,12 +1119,7 @@ export class Provider extends events.EventEmitter {
   readonly issuer: string;
   readonly app: Koa;
 
-  env?: Koa['env'];
   proxy?: Koa['proxy'];
-  subdomainOffset?: number;
-  proxyIpHeader?: string;
-  maxIpsCount?: number;
-  keys?: Koa['keys'];
   listen: Koa['listen'];
   callback: Koa['callback'];