Cleaned up OAUTH2 login logic.

Author: gmessner

src/main/java/org/gitlab4j/api/AbstractApi.java

@@ -21,7 +21,7 @@
  */
 public abstract class AbstractApi implements Constants {
 
-    private final GitLabApi gitLabApi;
+    protected final GitLabApi gitLabApi;
 
     public AbstractApi(GitLabApi gitLabApi) {
         this.gitLabApi = gitLabApi;

src/main/java/org/gitlab4j/api/GitLabApi.java

@@ -33,7 +33,7 @@ public class GitLabApi {
 
     /** Specifies the version of the GitLab API to communicate with. */
     public enum ApiVersion {
-        V3, V4, OAUTH2_CLIENT;
+        V3, V4;
 
         public String getApiNamespace() {
             return ("/api/" + name().toLowerCase());
@@ -268,7 +268,10 @@ public static GitLabApi oauth2Login(ApiVersion apiVersion, String url, String us
             throw new IllegalArgumentException("both username and email cannot be empty or null");
         }
 
-        GitLabApi gitLabApi = new GitLabApi(ApiVersion.OAUTH2_CLIENT, url, (String)null);
+        // Create a GitLabApi instance set up to be used to do an OAUTH2 login.
+        GitLabApi gitLabApi = new GitLabApi(apiVersion, url, (String)null);
+        gitLabApi.apiClient.setHostUrlToBaseUrl();
+
         if (ignoreCertificateErrors) {
             gitLabApi.setIgnoreCertificateErrors(true);
         }

src/main/java/org/gitlab4j/api/GitLabApiClient.java

@@ -210,9 +210,7 @@ public GitLabApiClient(ApiVersion apiVersion, String hostUrl, TokenType tokenTyp
         // Remove the trailing "/" from the hostUrl if present
         this.hostUrl = (hostUrl.endsWith("/") ? hostUrl.replaceAll("/$", "") : hostUrl);
         this.baseUrl = this.hostUrl;
-        if (ApiVersion.OAUTH2_CLIENT != apiVersion) {
-            this.hostUrl += apiVersion.getApiNamespace();
-        }
+        this.hostUrl += apiVersion.getApiNamespace();
 
         this.tokenType = tokenType;
         this.authToken = authToken;
@@ -760,6 +758,13 @@ protected Invocation.Builder invocation(URL url, MultivaluedMap<String, String>
         return (builder);
     }
 
+    /**
+     * Used to set the host URL to be used by OAUTH2 login in GitLabApi.
+     */
+    void setHostUrlToBaseUrl() {
+        this.hostUrl = this.baseUrl;
+    }
+
     /**
      * Returns true if the API is setup to ignore SSL certificate errors, otherwise returns false.
      *