Node connection validation improvements

[ogabrielluiz]

This comment by @ScripterSugar points out that our approach to validating connection between nodes might need some improvements:
#47 (comment)

Specifically this part:

We also need to fix hard-coded "type:str" notation on ParameterComponent. I'd like to also find a way to actually use type parameter rather than just parse handle's id field when we're validating connections between nodes (Because current implementation is eager to be broken in future if we try to introduce way to manage custom components. Using reserved eparators for component ID will break the validation), but I'm not sure that's doable as this is my first time using reactflow library.

I'd like to hear @anovazzi1 and @lucaseduoli 's opinions on this matter.

[lucaseduoli]

The hard-coded "type:str" on the output of the nodes was exclusively implemented to make connections with the Chat Output and the String node, for concatenation. Since both nodes are not present on the present version, that type is not necessary anymore. We can remove it for now.

[lucaseduoli]

My original thought was that all of the functions of the LangChain library output a string to be printed or used by other functions. That's why I hard-coded the str type into it. But, if we don't use this type for anything else, we can remove it with no problems.

[ogabrielluiz]

We can set up an issue for that. Thanks, @lucaseduoli!

About the custom components.. we will still be required to setup types that interact well with LangChain in the beginning, so Tools are python functions which use str as input and output, and possibly other types that inherit from Chain or Memory, etc.

The first step would be to set up tools as these are very important to increase LangFlow's power compared to LangChain's.
To do that we most likely will create a text area that validates the function in the backend once saved and uses it to make the prediction.