Add web client and minor refactor

src/main/java/io/cryostat/net/OpenShiftAuthManager.java

@@ -108,11 +108,10 @@ public class OpenShiftAuthManager extends AbstractAuthManager {
         this.clientProvider = clientProvider;
         this.webClient = webClient;
         try {
-            authorizationUrl = this.computeAuthorizationEndpoint();
+            authorizationUrl = this.computeAuthorizationEndpoint().get();
         } catch (ExecutionException | InterruptedException e) {
             logger.error("OAuth endpoint retrieval failed", e.getMessage());
-            //throw new IOException(
-            //        "OAuth server unreachable", e); // how to handle exceptions properly?
+            // how to handle exceptions properly?
         }
     }
 
@@ -318,7 +317,8 @@ public static String getAuthorizationEndpoint() {
         return authorizationUrl;
     }
 
-    private String computeAuthorizationEndpoint() throws ExecutionException, InterruptedException {
+    private Future<String> computeAuthorizationEndpoint()
+            throws ExecutionException, InterruptedException {
         CompletableFuture<JsonObject> oauthMetadata = new CompletableFuture<>();
         CompletableFuture<String> authUrl = new CompletableFuture<>();
 
@@ -336,7 +336,7 @@ private String computeAuthorizationEndpoint() throws ExecutionException, Interru
                         });
 
         authUrl.complete(oauthMetadata.get().getString(OAUTH_ENDPOINT_KEY) + OAUTH_REQ_PARAMS);
-        return authUrl.get();
+        return authUrl;
     }
 
     @SuppressFBWarnings(

src/main/java/io/cryostat/net/web/http/api/v2/EmptyOpenShiftTokenException.java

@@ -41,6 +41,6 @@
 
 public class EmptyOpenShiftTokenException extends IOException {
     public EmptyOpenShiftTokenException() {
-        super("Token cannot be empty");
+        super("Token is empty");
     }
 }