Add basic memory-based session driver

src/http/session/Session.ts

@@ -0,0 +1,39 @@
+import {Injectable, Inject} from "@extollo/di"
+import {ErrorWithContext} from "@extollo/util"
+import {Request} from "../lifecycle/Request"
+
+export type SessionData = {[key: string]: any}
+
+export class NoSessionKeyError extends ErrorWithContext {
+    constructor() {
+        super('No session ID has been set.')
+    }
+}
+
+export class SessionNotLoadedError extends ErrorWithContext {
+    constructor() {
+        super('Cannot access session data; data is not loaded.')
+    }
+}
+
+@Injectable()
+export abstract class Session {
+    @Inject()
+    protected readonly request!: Request
+
+    public abstract getKey(): string
+
+    public abstract setKey(key: string): void
+
+    public abstract load(): void | Promise<void>
+
+    public abstract persist(): void | Promise<void>
+
+    public abstract getData(): SessionData
+
+    public abstract setData(data: SessionData): void
+
+    public abstract get(key: string, fallback?: any): any
+
+    public abstract set(key: string, value: any): void
+}