Preserve per-source pacing across queue jobs and add source pause

scraper/sources/mangadex.js

@@ -8,7 +8,7 @@ const { controlledHttp } = require('./common');
 module.exports = {
   id: 'mangadex', label: 'MangaDex', match: mangaDexInfo,
   async discover(item, options) {
-    const http = new SlowHttp({ minMs: options.settings.minMs, maxMs: options.settings.maxMs,
+    const http = new SlowHttp({ gateKey: 'mangadex', minMs: options.settings.minMs, maxMs: options.settings.maxMs,
       maxRetries: 2, userAgent: 'MangaCircus-Scraper/1.0 (personal archival; sequential MangaDex requests)',
       onEvent: options.onEvent });
     return discoverMangaDexCatalog(item.url, controlledHttp(http, options.shouldStop));