Make EML system attribute configurable in AppModel

Fixes #441

src/js/models/AppModel.js

@@ -421,6 +421,21 @@ define(['jquery', 'underscore', 'backbone'],
       * @since 2.13.0
       */
       editorSchemaLocation: "https://eml.ecoinformatics.org/eml-2.2.0 https://eml.ecoinformatics.org/eml-2.2.0/eml.xsd",
+
+      /**
+       * The text to use for the eml system attribute. The system attribute
+       * indicates the data management system within which an identifier is in
+       * scope and therefore unique. This is typically a URL (Uniform Resource
+       * Locator) that indicates a data management system.  All identifiers that
+       * share a system must be unique. In other words, if the same identifier
+       * is used in two locations with identical systems, then by definition the
+       * objects at which they point are in fact the same object.
+       * @type {string}
+       * @since x.x.x
+       * @link https://eml.ecoinformatics.org/schema/eml-resource_xsd#SystemType
+       * @link https://eml.ecoinformatics.org/schema/eml_xsd
+       */
+      emlSystem: "knb",
 
       /**
       * This error message is displayed when the Editor encounters an error saving

src/js/models/metadata/eml211/EML211.js

@@ -2095,6 +2095,10 @@ define(['jquery', 'underscore', 'backbone', 'uuid',
 
       /* Initialize the object XML for brand spankin' new EML objects */
       createXML: function() {
+
+          let emlSystem = MetacatUI.appModel.get("emlSystem");
+          emlSystem = (!emlSystem || typeof emlSystem != "string") ? "knb" : emlSystem;
+
           var xml = "<eml:eml xmlns:eml=\"https://eml.ecoinformatics.org/eml-2.2.0\"></eml:eml>",
               eml = $($.parseHTML(xml));
 
@@ -2103,7 +2107,7 @@ define(['jquery', 'underscore', 'backbone', 'uuid',
               eml.attr("xmlns:stmml", "http://www.xml-cml.org/schema/stmml-1.1");
               eml.attr("xsi:schemaLocation", "https://eml.ecoinformatics.org/eml-2.2.0 https://eml.ecoinformatics.org/eml-2.2.0/eml.xsd");
               eml.attr("packageId", this.get("id"));
-              eml.attr("system", "knb"); // We could make this configurable at some point
+              eml.attr("system", emlSystem);
 
               // Add the dataset
               eml.append(document.createElement("dataset"));