Implement directory-based plugin system (#4548)

* Implement directory-based plugin system

* Fix Selenium test

---------

Co-authored-by: Nicholas Tindle <nick@ntindle.com>
Co-authored-by: Merwane Hamadi <merwanehamadi@gmail.com>

scripts/install_plugin_deps.py

@@ -2,6 +2,7 @@ import os
 import subprocess
 import sys
 import zipfile
+from glob import glob
 from pathlib import Path
 
 
@@ -16,6 +17,8 @@ def install_plugin_dependencies():
         None
     """
     plugins_dir = Path(os.getenv("PLUGINS_DIR", "plugins"))
+
+    # Install zip-based plugins
     for plugin in plugins_dir.glob("*.zip"):
         with zipfile.ZipFile(str(plugin), "r") as zfile:
             try:
@@ -30,6 +33,13 @@ def install_plugin_dependencies():
             except KeyError:
                 continue
 
+    # Install directory-based plugins
+    for requirements_file in glob(f"{plugins_dir}/*/requirements.txt"):
+        subprocess.check_call(
+            [sys.executable, "-m", "pip", "install", "-r", requirements_file],
+            stdout=subprocess.DEVNULL,
+        )
+
 
 if __name__ == "__main__":
     install_plugin_dependencies()