Ability to tell Orquesta to treat a variable as raw string and not do any (YAQL and Jinja) processing on it

I was debugging an Orquesta flow and I initially thought it was a bug in Orquesta (due to the error message), but it turns out that the bug is related to dynamically retrieved data containing a YAQL expression.

It's fairly common scenario that data inside workflows is retrieved dynamically and this data could potentially contain Jinja or YAQL escape sequence (think Jinja / YAQL injection).

Here is an example workflow where this issue can arise - https://github.com/StackStorm/stackstorm-st2community/blob/master/actions/workflows/retrieve_data_and_send_daily_stats_to_slack.yaml

github_data and / or forum_posts can contain YAQL and Jinja expression and assemble_message task would fail publishing message variable since it would try to render it as YAQL / Jinja and this would fail due to variable not being defined - https://github.com/StackStorm/stackstorm-st2community/blob/master/actions/workflows/retrieve_data_and_send_daily_stats_to_slack.yaml#L46.

Yes, I could process / escape this data inside st2community.assemble_message (and that's what I will do until a better solution is in place), but I think we should provide an Orquesta level feature for handling that.

Pretty much all the programming languages and templating libraries provide some kind of way to treat a value as raw string / escape it and not do any processing on it and I think that's what we need in Orquesta as well (ability to mark a variable as raw so it's not processed).

I also think that's important from security perspective because there are a lot of scenarios where data is retrieved dynamically or passed in by a user.

I'm also open to suggestions (aka if this can already be solved in some other way).

Use the referenced stackstorm-st2community/actions/workflows/retrieve_data_and_send_daily_stats_to_slack.yaml workflow as the entry point, especially the assemble_message task and its message variable. Trace how dynamically retrieved values reach YAQL and Jinja processing; completion would be a defined raw-string mechanism that prevents both renderers from evaluating marked values, with coverage for the example behavior.