Bug: URL and Identifier system not being correctly set when mapping_set_id not generated

[joeflack4]

Overview

If choosing a static mapping_set_id in the inputs (which is what we want to do; see #4), the url that gets created is wrong. And because that is wrong, the identifier.system also is wrong. See example below. This is the result of me setting a # mapping_set_id: "fa10c6d4-614c-4762-93e4-782d86eede41" in the metadata comment of the input TSV.

Example:

 {
   "resourceType": "ConceptMap",
-  "url": "https://w3id.org/sssom/mappings/fa10c6d4-614c-4762-93e4-782d86eede41",
+  "url": "fa10c6d4-614c-4762-93e4-782d86eede41",
   "identifier": [
     {
-      "system": "https://w3id.org/sssom/mappings/",
-      "value": "https://w3id.org/sssom/mappings/fa10c6d4-614c-4762-93e4-782d86eede41"
+      "system": "/",
+      "value": "fa10c6d4-614c-4762-93e4-782d86eede41"
     }
   ],
   "name": "fa10c6d4-614c-4762-93e4-782d86eede41",