fix: update DifyPluginEnv to set default for REMOTE_INSTALL_URL (#142)

* feat: update DifyPluginEnv to set default for REMOTE_INSTALL_URL and add unit tests for environment configurations

- Set default value of REMOTE_INSTALL_URL to None in DifyPluginEnv.
- Introduced unit tests for various installation methods including local, remote, and serverless configurations, ensuring proper functionality without parameters and with specific settings.

* fix: update condition for install_url check in Plugin class

- Changed the condition to explicitly check for None instead of a truthy value, improving clarity and preventing potential issues with falsy values.

* apply ruff

Author: Yeuoly

python/tests/config/test_config.py

@@ -0,0 +1,51 @@
+from dify_plugin.config.config import DifyPluginEnv, InstallMethod
+
+
+def test_launch():
+    """
+    Env should works without any parameters and env variables
+    """
+    env = DifyPluginEnv()
+
+    assert InstallMethod.Local == env.INSTALL_METHOD
+
+
+def test_launch_local_plugin():
+    """
+    Env should works without any parameters and env variables
+    """
+    env = DifyPluginEnv(
+        INSTALL_METHOD=InstallMethod.Local,
+    )
+
+    assert InstallMethod.Local == env.INSTALL_METHOD
+
+
+def test_launch_remote_plugin():
+    """
+    Env should works with remote install url and key
+    """
+    env = DifyPluginEnv(
+        INSTALL_METHOD=InstallMethod.Remote,
+        REMOTE_INSTALL_URL="debug.dify.ai:5003",
+        REMOTE_INSTALL_KEY="19dcf2f3-2856-4fa4-b32b-9ece9b741977",
+    )
+
+    assert InstallMethod.Remote == env.INSTALL_METHOD
+    assert env.REMOTE_INSTALL_URL == "debug.dify.ai:5003"
+    assert env.REMOTE_INSTALL_KEY == "19dcf2f3-2856-4fa4-b32b-9ece9b741977"
+
+
+def test_launch_serverless_plugin():
+    """
+    Env should works with serverless install method
+    """
+    env = DifyPluginEnv(
+        INSTALL_METHOD=InstallMethod.Serverless,
+        SERVERLESS_HOST="0.0.0.0",
+        SERVERLESS_PORT=8080,
+    )
+
+    assert InstallMethod.Serverless == env.INSTALL_METHOD
+    assert env.SERVERLESS_HOST == "0.0.0.0"
+    assert env.SERVERLESS_PORT == 8080