feat: add --time-format parameter for parse and search commands

[digizeph]

Summary

Add --time-format parameter to monocle parse and monocle search commands to control how timestamps are displayed in output.

Features

• --time-format unix (default): Output timestamps as Unix epoch (integer or float)
  • Example: 1697043600 or 1697043600.5
• --time-format rfc3339: Output timestamps in ISO 8601/RFC3339 format
  • Example: 2023-10-11T17:00:00+00:00

Usage Examples

Together with --format table and --fields timestamp,prefix,as_path, the updated command results can look much cleaner:

monocle search -t 2024-01-01 -d 1s -c route-views3 -p 140.99.244.0/23,201.87.136.0/24 --time-format rfc3339 --format table --fields timestamp,prefix,as_path`
╭─────────────────────────────────────┬─────────────────┬──────────────────────────────────────────────╮
│ timestamp                           │ prefix          │ as_path                                      │
├─────────────────────────────────────┼─────────────────┼──────────────────────────────────────────────┤
│ 2024-01-01T00:00:00.177294969+00:00 │ 140.99.244.0/23 │ 209 3356 3223 20068                          │
│ 2024-01-01T00:00:00.563082933+00:00 │ 140.99.244.0/23 │ 23367 1299 3356 3223 20068                   │
│ 2024-01-01T00:00:00.617777109+00:00 │ 201.87.136.0/24 │ 6939 52320 28598 265303 265303 265303 265303 │
╰─────────────────────────────────────┴─────────────────┴──────────────────────────────────────────────╯

Backward Compatibility

• Default behavior unchanged: --time-format unix is the default, maintaining existing output format
• JSON output unaffected: JSON output always uses numeric Unix timestamps regardless of --time-format setting, ensuring backward compatibility for scripts that parse JSON output
• Non-breaking: All existing command invocations continue to work identically

Implementation Details

• Added TimestampFormat enum to src/lens/utils.rs with variants Unix and Rfc3339
• Updated elem_format.rs to support timestamp formatting via get_field_value_with_time_format()
• Added --time-format CLI argument to both parse.rs and search.rs commands
• JSON output functions (build_json_object) continue to use json!(elem.timestamp) to preserve numeric output