Move view function into own file, add test

app/main/views/api_keys.py

@@ -0,0 +1,9 @@
+from flask import render_template
+from flask_login import login_required
+from app.main import main
+
+
+@main.route("/services/<int:service_id>/api-keys")
+@login_required
+def api_keys(service_id):
+    return render_template('views/api-keys.html', service_id=service_id)