Rewrite [DynamicXml] and [DynamicYaml] badges (#2487)

- A little related cleanup in `server.js`: remove a couple import renames.

services/dynamic/dynamic-xml.service.js

@@ -0,0 +1,63 @@
+'use strict'
+
+const { DOMParser } = require('xmldom')
+const xpath = require('xpath')
+const BaseService = require('../base')
+const { InvalidResponse } = require('../errors')
+const {
+  createRoute,
+  queryParamSchema,
+  errorMessages,
+  renderDynamicBadge,
+} = require('./dynamic-helpers')
+
+// This service extends BaseService because it uses a different XML parser
+// than BaseXmlService which can be used with xpath.
+//
+// One way to create a more performant version would be to use the BaseXml
+// JSON parser and write the queries in jsonpath instead. Then eventually
+// deprecate the old version.
+module.exports = class DynamicXml extends BaseService {
+  static get category() {
+    return 'dynamic'
+  }
+
+  static get route() {
+    return createRoute('xml')
+  }
+
+  static get defaultBadgeData() {
+    return {
+      label: 'custom badge',
+    }
+  }
+
+  async handle(namedParams, queryParams) {
+    const {
+      url,
+      query: pathExpression,
+      prefix,
+      suffix,
+    } = this.constructor._validateQueryParams(queryParams, queryParamSchema)
+
+    const pathIsAttr = pathExpression.includes('@')
+
+    const { buffer } = await this._request({
+      url,
+      options: { headers: { Accept: 'application/xml, text/xml' } },
+      errorMessages,
+    })
+
+    const parsed = new DOMParser().parseFromString(buffer)
+
+    const values = xpath
+      .select(pathExpression, parsed)
+      .map((node, i) => (pathIsAttr ? node.value : node.firstChild.data))
+
+    if (!values.length) {
+      throw new InvalidResponse({ prettyMessage: 'no result' })
+    }
+
+    return renderDynamicBadge({ values, prefix, suffix })
+  }
+}