[KED-1537] Allow a node input to be a literal value.

I think kedro should add the way to pass a literal to a node, just like they did with param:. Maybe something like literal: or string: and int:

__Originally posted by @sansagara in https://github.com/quantumblacklabs/kedro/issues/213#issuecomment-698932788__

[Galileo-Galilei]

Hello,

*Disclaimer to the OP: Sorry for the downvote, it is the only way to say that I am against implementing this feature but no offense intended, it is absolutely not personal.

I totally support @WaylonWalker point of view here for everal reasons:

• I understand why someone want to do this (mainly to iterate faster during their exploration phase), but this will very encourage bad software engineering practice (i.e. tighten compute and configuration by not using a conf file).
• I know it sounds a bit harsh but I don’t think this feature request is in line with Kedro’s principles (i.e. enforces SE best practices as much as possible).
• Since the little hack with lamba suggested by @WaylonWalker already works well, I don’t feel it would improve much user experience.
• This feature will also prevent to track the parameter with a specific name, for logging in mlflow for instance (ok this one is self interested 😇)

[WaylonWalker]

This would make things simpler, but it is currently possible using partial or lambda functions. See my comment on the previous issue https://github.com/quantumblacklabs/kedro/issues/213#issuecomment-699509279.

If this were implemented I would fear that it would make doing bad things too easy. The current design makes doing the right thing easy (loading from the catalog or params) and doing borderline things possible. I would hate to see a pipeline completely bypass the catalog and pass DataFrames directly into the node.