Make LDAP connection thread safe

Add open() and close() methods to LDAP Client.

README.md

@@ -21,10 +21,10 @@ Create a new virtualenv and run `pip install .` inside of it.
 >>>
 >>> from phi.ldap.client import Client
 >>> ldap_client = Client(**ldap_config)
->>>
+>>> ldap_client.open()
->>> from phi.ldap.connection import open_connection
->>> open_connection(ldap_client.connection)
 >>>
 >>> from phi.ldap.commands import whoami
 >>> whoami(client)
+>>>
+>>> ldap_client.close()
 ```

src/phi/ldap/client.py

@@ -1,7 +1,9 @@
+from threading import Lock
 from ldap3.utils.log import set_library_log_detail_level, PROTOCOL
 
 from phi.logging import get_logger
 from phi.ldap.connection import make_connection
+from phi.ldap.connection import open_connection, close_connection
 
 log = get_logger(__name__)
 set_library_log_detail_level(PROTOCOL)
@@ -21,9 +23,25 @@ class Client:
         self.password = password
         self.base_dn = base_dn
 
+        self.connection_lock = Lock()
         self.connection = make_connection(host=self.host, port=self.port,
                                           encryption=self.encryption,
                                           ciphers=self.ciphers,
                                           validate=self.validate,
                                           username=self.username,
                                           password=self.password)
+
+    def open(self):
+        self.connection_lock.acquire()
+        if self.connection.closed is True:
+            open_connection(self.connection)
+        else:
+            self.connection_lock.release()
+            raise Exception("Connection is already open. "
+                            "Cannot open again.")
+        self.connection_lock.release()
+
+    def close(self):
+        self.connection_lock.acquire()
+        close_connection(self.connection)
+        self.connection_lock.release()