SONAR-7678 server-side stateless settings

* Settings class becomes abstract as multiple implementations
are used. Can't become an interface for binary
backward-compatibility of API

* tests should use MapSettings, an in-memory implementation
of Settings

* web server uses a thread-specific cache of settings when
processing HTTP requests

* web server does not have a cache of settings during startup,
except for the system settings loaded from sonar.properties

* Compute Engine uses a thread-specific cache of settings when
  processing a task. Cache is clear at end of task.

 * some useless methods of PersistentSettings are removed

1 files changed, 3 insertions, 1 deletions

diff --git a/it/it-plugins/security-plugin/src/test/java/FakeAuthenticatorTest.java b/it/it-plugins/security-plugin/src/test/java/FakeAuthenticatorTest.java
index 6a0b1884a05..577033fe27d 100644
--- a/it/it-plugins/security-plugin/src/test/java/FakeAuthenticatorTest.java
+++ b/it/it-plugins/security-plugin/src/test/java/FakeAuthenticatorTest.java
@@ -17,9 +17,11 @@
  * along with this program; if not, write to the Free Software Foundation,
  * Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
  */
+
 import java.util.Map;
 import org.junit.Before;
 import org.junit.Test;
+import org.sonar.api.config.MapSettings;
 import org.sonar.api.config.Settings;
 import org.sonar.api.security.UserDetails;
 
@@ -33,7 +35,7 @@ public class FakeAuthenticatorTest {
 
   @Before
   public void setUp() {
-    settings = new Settings();
+    settings = new MapSettings();
     authenticator = new FakeAuthenticator(settings);
     authenticator.init();
   }