better subdomain collision message

Author: mcanoy

src/main/java/com/redhat/labs/lodestar/hosting/service/HostingService.java

@@ -189,7 +189,7 @@ public String updateHosting(String engagementUuid, List<HostingEnvironment> host
             }
 
             if(hostingEnv.getOcpSubDomain() != null && !isValidSubdomain(engagementUuid, hostingEnv.getOcpSubDomain())) {
-                String message = String.format("Subdomain name %s is invalid", hostingEnv.getOcpSubDomain());
+                String message = String.format("Subdomain %s has been taken by another engagement", hostingEnv.getOcpSubDomain());
                 throw new WebApplicationException(Response.status(409).entity(Map.of("lodestarMessage", message)).build());
             }
             fillOutHostingEnvironment(hostingEnv, engagement.getUuid(), engagement.getRegion(), engagement.getProjectId());

src/test/java/com/redhat/labs/lodestar/hosting/resource/HostingResourceTest.java

@@ -61,7 +61,7 @@ void testUsedSubdomainUpdateByUuid() {
         he.get(0).setOcpSubDomain("red-1");
 
         given().contentType(ContentType.JSON).pathParam("engagementUuid", "second").body(he).put("/engagements/{engagementUuid}").then()
-                .statusCode(409).body("lodestarMessage", equalTo("Subdomain name red-1 is invalid"));
+                .statusCode(409).body("lodestarMessage", equalTo("Subdomain red-1 has been taken by another engagement"));
     }
 
     @Test