[PoC] Labs metadata

See databricks/cli#637 for more context

install.py

@@ -0,0 +1,3 @@
+import os
+
+print(f'host is {os.environ["DATABRICKS_HOST"]}')

labs.yml

@@ -0,0 +1,22 @@
+---
+name: dbx
+context: workspace
+description: Databricks CLI extensions
+hooks:
+  install: install.py
+entrypoint: main.py
+commands:
+  - name: foo
+    description: foo command
+    flags:
+      - name: first
+        description: first flag description
+      - name: second
+        description: second flag description
+  - name: bar
+    description: bar command
+    flags:
+      - name: first
+        description: first flag description
+      - name: second
+        description: second flag description

main.py

@@ -0,0 +1,14 @@
+import os, sys, json
+
+print(f'host is {os.environ["DATABRICKS_HOST"]}')
+
+payload = json.loads(sys.argv[1])
+print(f'[{payload["command"]}]: flags are {payload["flags"]}')
+
+answer = input('What is your name? ')
+
+print(f'got answer: {answer}')
+
+answer = input('Preferences? ')
+
+print(f'got answer: {answer}')