Support scenario of Registry header secret content being a multiline array
The following discussion from !1383 (merged) should be addressed:
cathere limits us with what we can use as a secret value.
We need to pass an array, but our sed won't work with a multiline, so we only support the string literal
We should log a followup issue to see how we can better deal with this. Probably needs to somewhat more like the storage solution where we indent our secret content, insert it after the secret filename, then remove the filename. But that might break the string literal form? Anyways, I think we should deal with it in a followup.