feat(oauth): add OAuth token support

ts/bunq.classes.apicontext.ts

@@ -9,6 +9,7 @@ export interface IBunqApiContextOptions {
   environment: 'SANDBOX' | 'PRODUCTION';
   deviceDescription: string;
   permittedIps?: string[];
+  isOAuthToken?: boolean;
 }
 
 export class BunqApiContext {
@@ -43,6 +44,15 @@ export class BunqApiContext {
    * Initialize the API context (installation, device, session)
    */
   public async init(): Promise<void> {
+    // If using OAuth token, skip session creation
+    if (this.options.isOAuthToken) {
+      // OAuth tokens already have an associated session
+      this.context.sessionToken = this.options.apiKey;
+      this.session = new BunqSession(this.crypto, this.context);
+      this.session.setOAuthMode(true);
+      return;
+    }
+    
     // Try to load existing context
     const existingContext = await this.loadContext();
     
@@ -125,6 +135,11 @@ export class BunqApiContext {
    * Refresh session if needed
    */
   public async ensureValidSession(): Promise<void> {
+    // OAuth tokens don't need session refresh
+    if (this.options.isOAuthToken) {
+      return;
+    }
+    
     await this.session.refreshSession();
     await this.saveContext();
   }