fix(job): ensure agenda is ready before calling save job

Author: simllll

src/Job.ts

@@ -170,6 +170,8 @@ export class Job<DATA = any | void> {
 	}
 
 	async save(): Promise<Job> {
+		// ensure db connection is ready
+		await this.agenda.ready;
 		return this.agenda.db.saveJob(this);
 	}
 

src/index.ts

@@ -63,7 +63,7 @@ export class Agenda extends EventEmitter {
 
 	private jobProcessor?: JobProcessor;
 
-	private ready: Promise<void>;
+	readonly ready: Promise<void>;
 
 	async getRunningStats(fullDetails = false): Promise<IAgendaStatus> {
 		if (!this.jobProcessor) {