trigger_comment may screw pipelinerun yaml with the the newline

[chmouel]

when we have a yaml with the {{trigger_comment}} expansion variable we may end up with bad yaml:

for example this pipelinerun:

apiVersion: tekton.dev/v1
kind: PipelineRun
metadata:
  name: prow-commands
  annotations:
    pipelinesascode.tekton.dev/pipeline: "https://raw.githubusercontent.com/openshift-pipelines/pac-boussole/main/pipeline-boussole.yaml"
    pipelinesascode.tekton.dev/on-comment: "^/(hello|merge|help|lgtm|(assign|unassign|label|unlabel)[ ].*)$"
    pipelinesascode.tekton.dev/max-keep-runs: "2"
spec:
  params:
    - name: trigger_comment
      value: |
        {{ trigger_comment }}
    - name: repo_owner
      value: "{{ repo_owner }}"
    - name: repo_name
      value: "{{ repo_name }}"
    - name: pull_request_number
      value: "{{ pull_request_number }}"
    - name: pull_request_sender
      value: "{{ body.issue.user.login }}"
    - name: git_auth_secret
      value: "{{ git_auth_secret }}"
    - name: comment_sender
      value: "{{ sender }}"
  pipelineRef:
    name: boussole

if i do a github comment with newlines like this

/help

it will be expanded to this:

and then we get a parser error:

because it's not a yaml anymore..

I suggest we change the trigger_comment to expand the \r\n to real \n the same way we do for pull_requests_labels:

https://pipelinesascode.com/docs/guide/matchingevents/#matching-pipelinerun-to-a-pull-request-labels

and let the user do it from their script... since there is no reliable way to do this and this is prone to bad user input interpolation