Display build date in UI, injected during CI build

app/app.py

@@ -8,6 +8,8 @@ from concurrent.futures import ThreadPoolExecutor, as_completed
 
 import paramiko
 
+BUILD_DATE = '__BUILD_DATE__'
+
 from flask import Flask, render_template, jsonify
 from flask_sqlalchemy import SQLAlchemy
 
@@ -272,7 +274,7 @@ def index():
     for g in groups:
         groups[g].sort(key=lambda s: _ip_sort_key(s.primary_ip))
 
-    return render_template('index.html', groups=groups)
+    return render_template('index.html', groups=groups, build_date=BUILD_DATE)
 
 
 @app.route('/api/servers')