feature request: allow for generic feedback text

[moloko]

A lot of the time I see question feedback in Adapt that's along the lines of:

"_feedback": {
    "correct": "That's correct. This is some additional text explaining why the answer is what it is.",
    "_incorrect": {
        "final": "Your answer was incorrect. This is some additional text explaining why the answer is what it is."
    },
    "_partlyCorrect": {
        "final": "Your answer was partly correct. This is some additional text explaining why the answer is what it is."
    }
}

To that end, I wonder if we could save content authors (and translators) a fair bit of time and effort by allowing for something like this:

"_feedback": {
    "generic": "This is some additional text explaining why the answer is what it is.",
    "correct": "That's correct. {{{generic}}}",
    "_incorrect": {
        "final": "Your answer was incorrect. {{{generic}}}"
    },
    "_partlyCorrect": {
        "final": "Your answer was partly correct. {{{generic}}}"
    }
}

[oliverfoster]

there's a large discussion on how _feedback is insufficient if you could have a look as see if it's worth pulling it into this discussion?

#1469
@amruta-thakur has a really nice idea of removing feedback from the core in its entirety

[chucklorenz]

If I understand your approach, authors could choose not to use {{{generic}}} and to continue to write as current. That would be helpful, I think, for implementation in the AAT--because it wouldn't have to be implemented. For the course authors I support who use the AAT, the variations of feedback cause ongoing confusion. I'd prefer not to increase that with another option--unless it can be done in the AAT with some "elegance". But I see plenty of room for this as a shortcut for FW authors.

[chucklorenz]

Another minor suggestion. To me "generic" sounds like another category of feedback alongside "correct" and "incorrect". Perhaps we avoid that bit of confusion by using a word/phrase that hints at it being an included part, something along the lines of "repeatedText" or "common".