Affected Issue(s): #606 (#612)

What this commit has achieved:
1. Externalized location of "mdm-rules.json" in the `AppProperties`
2. More info about the `ResourceLoader` interface is available at
https://docs.spring.io/spring-framework/reference/core/resources.html#resources-resourceloader

src/main/resources/application.yaml

@@ -137,6 +137,7 @@ hapi:
     #    graphql_enabled: true
     narrative_enabled: false
     mdm_enabled: false
+    mdm_rules_json_location: "mdm-rules.json"
     #    local_base_urls:
     #      - https://hapi.fhir.org/baseR4
     #    partitioning: