union() doesn't work for context items

[saig0]

Describe the bug
The built-in function union doesn't filter duplicates for a list of context items.

union([{x:1},{y:2}],[{x:1}, {z:3}])

To Reproduce
Steps to reproduce the behavior:

1. Evaluate the expression

union([{x:1},{y:2}],[{x:1}, {z:3}])

2. Verify that the result contains {x:1} twice

Expected behavior
The function union() should filter duplicates for a list of context items.

union([{x:1},{y:2}],[{x:1}, {z:3}])
// [{"x":1},{"y":2}, {"z":3}]

Environment

• FEEL engine version: 1.17.3
• Affects:
  • Camunda Automation Platform 7: [7.x]
  • Zeebe broker: 8.3.3
• Support case: https://jira.camunda.com/browse/SUPPORT-23030