YAML input in trigger UI

### Description

I work in a project where having a yaml input in the web UI (instead of json -> which is in the case of object type param) is beneficial.

I understand that airflow support multiple datatypes - ints, strings, list/arrays, and objects.
Is it possible to also have yaml as a input.

On a sidenote: I thought of interpreting multiline input, i.e., list of strings as my input, which I can join and interpret as yaml.
However, airflow tends to remove trailing white spaces in string list items, thereby losing indentation information.
example:

a multiline array input of
```
a:
b: c
```

is incorrectly transformed to yaml of this form:
```yaml
{a: None, b: c}
```
instead of:
```yaml
{a: {b: c}}
```

is this the intended purpose or is this is a bug??

### Use case/motivation

I would like a human readable input, where the user can copy paste their yaml files in a text box.

### Related issues

I thought of interpreting multiline input, i.e., list of strings as my input, which I can join and interpret as yaml.
However, airflow tends to remove trailing white spaces in string list items, thereby losing indentation information.
### Are you willing to submit a PR?

- [ ] Yes I am willing to submit a PR!

### Code of Conduct

- [x] I agree to follow this project's [Code of Conduct](https://github.com/apache/airflow/blob/main/CODE_OF_CONDUCT.md)

No file or test is named in the issue. Start by tracing the trigger UI's handling of object and multiline inputs, then verify how whitespace and indentation are preserved; the work is done when a user can paste human-readable YAML into the UI without losing its nesting.

Written by the indexing model from the issue text.