Create SQL data source utils class

- Extract logic used in SQLite and MySQL for logging and closing SQL objects
    - Decided to leave buildAuthFromResultSet methods individually as this might be more implementation-specific
- Rename DataSource#close to DataSource#closeConnection to fix conflict with static import

src/test/java/fr/xephi/authme/datasource/SqlDataSourceUtilsTest.java

@@ -0,0 +1,135 @@
+package fr.xephi.authme.datasource;
+
+import fr.xephi.authme.TestHelper;
+import org.junit.Before;
+import org.junit.Test;
+
+import java.sql.Connection;
+import java.sql.ResultSet;
+import java.sql.SQLException;
+import java.sql.Statement;
+import java.util.logging.Logger;
+
+import static org.hamcrest.Matchers.containsString;
+import static org.mockito.ArgumentMatchers.anyString;
+import static org.mockito.Mockito.doThrow;
+import static org.mockito.Mockito.mock;
+import static org.mockito.hamcrest.MockitoHamcrest.argThat;
+import static org.mockito.Mockito.verify;
+
+/**
+ * Test for {@link SqlDataSourceUtils}.
+ */
+public class SqlDataSourceUtilsTest {
+
+    private Logger logger;
+
+    @Before
+    public void initLogger() {
+        logger = TestHelper.setupLogger();
+    }
+
+    @Test
+    public void shouldHaveHiddenConstructor() {
+        TestHelper.validateHasOnlyPrivateEmptyConstructor(SqlDataSourceUtils.class);
+    }
+
+    @Test
+    public void shouldLogException() {
+        // given
+        String msg = "Hocus pocus did not work";
+        SQLException ex = new SQLException(msg);
+
+        // when
+        SqlDataSourceUtils.logSqlException(ex);
+
+        // then
+        verify(logger).warning(argThat(containsString(msg)));
+    }
+
+    @Test
+    public void shouldCloseStatement() throws SQLException {
+        // given
+        Statement st = mock(Statement.class);
+
+        // when
+        SqlDataSourceUtils.close(st);
+
+        // then
+        verify(st).close();
+    }
+
+    @Test
+    public void shouldHandleExceptionFromStatement() throws SQLException {
+        // given
+        Statement st = mock(Statement.class);
+        doThrow(SQLException.class).when(st).close();
+
+        // when
+        SqlDataSourceUtils.close(st);
+
+        // then
+        verify(logger).warning(anyString());
+    }
+
+    @Test
+    public void shouldCloseResultSet() throws SQLException {
+        // given
+        ResultSet rs = mock(ResultSet.class);
+
+        // when
+        SqlDataSourceUtils.close(rs);
+
+        // then
+        verify(rs).close();
+    }
+
+    @Test
+    public void shouldHandleExceptionFromResultSet() throws SQLException {
+        // given
+        ResultSet rs = mock(ResultSet.class);
+        doThrow(SQLException.class).when(rs).close();
+
+        // when
+        SqlDataSourceUtils.close(rs);
+
+        // then
+        verify(logger).warning(anyString());
+    }
+
+    @Test
+    public void shouldCloseConnection() throws SQLException {
+        // given
+        Connection con = mock(Connection.class);
+
+        // when
+        SqlDataSourceUtils.close(con);
+
+        // then
+        verify(con).close();
+    }
+
+    @Test
+    public void shouldHandleExceptionFromConnection() throws SQLException {
+        // given
+        Connection con = mock(Connection.class);
+        doThrow(SQLException.class).when(con).close();
+
+        // when
+        SqlDataSourceUtils.close(con);
+
+        // then
+        verify(logger).warning(anyString());
+    }
+
+    @Test
+    public void shouldHandleNullArgument() {
+        // given / when
+        SqlDataSourceUtils.close((Statement) null);
+        SqlDataSourceUtils.close((ResultSet) null);
+        SqlDataSourceUtils.close((Connection) null);
+
+        // then - nothing happens
+    }
+
+}