Allow setting debug mode from command line

Adds a --debug option to the command-line that enables debug mode
when running the sushy-emulator.
This should simplify debugging and development.

Change-Id: Ibf420dc3324b00548f55e4efd8610a61ded10dd3

releasenotes/notes/debug-mode-0dccdc3702c0590e.yaml

@@ -0,0 +1,5 @@
+---
+features:
+  - |
+    Adds an option --debug to enable debug mode when running sushy-emulator.
+

sushy_tools/emulator/main.py

@@ -779,6 +779,8 @@ def parse_args():
                         type=str,
                         help='Config file path. Can also be set via '
                              'environment variable SUSHY_EMULATOR_CONFIG.')
+    parser.add_argument('--debug', action='store_true',
+                        help='Enables debug mode when running sushy-emulator.')
     parser.add_argument('-i', '--interface',
                         type=str,
                         help='IP address of the local interface to listen '
@@ -819,6 +821,8 @@ def main():
 
     args = parse_args()
 
+    app.debug = args.debug
+
     if args.config:
         app.config.from_pyfile(args.config)