Right now when a pipeline is misspelled in the 'combination.weights' argument in the $rankFusion stage, the only feedback we get is that a specified pipeline is missing a weight.

Firstly, we could give some improved feedback here, as the current logic is not distinguishing between a pipeline being entirely absent, and being misspelled. Theres a couple possible improved suggestions we could give here:

• Print out the possible valid pipeline options that haven't been specified
• Do some simple text analysis between the provided nonexistent pipeline, and the possible remaining options (such as counting common in-order characters), and make a suggestion of what pipeline they meant  

Secondly, per SERVER-99674, well be changing the behavior to allow not all pipelines to be specified, so well need to change the feedback regardless.