Extend SNIHostName check to reject hostnames with trailing dot.

[resolves #656]

src/main/java/io/r2dbc/postgresql/client/SSLConfig.java

@@ -108,7 +108,7 @@ public static boolean isValidSniHostname(String input) {
                 return false;
             }
         }
-        return true;
+        return !input.endsWith(".");
     }
 
     //

src/test/java/io/r2dbc/postgresql/client/SSLConfigTests.java

@@ -0,0 +1,17 @@
+package io.r2dbc.postgresql.client;
+
+import org.junit.jupiter.api.Test;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * Unit tests for {@link SSLConfig}.
+ */
+final class SSLConfigTests {
+    @Test
+    public void testValidSniHostname(){
+        assertThat(SSLConfig.isValidSniHostname("example.com")).isEqualTo(true);
+        assertThat(SSLConfig.isValidSniHostname("example://.com")).isEqualTo(false);
+        assertThat(SSLConfig.isValidSniHostname("example.com.")).isEqualTo(false);
+    }
+}