Products and reactants should be selected from a list, not input as strings

[K20shores]

In the attached screenshot you can see that reactants and products are input as strings. This is brittle and will break if a species is input that doesn't exist for this mechanism, family in the database.

I would expect the species to be linked to reactions using uuids in the database or something similar so that when its name changes in the database it's immediately replicated in all reactions that that species is part of.

Acceptance Criteria

• Species for products and reactants are selected from a list for all reactions.
• Species stoichiometric coefficients are input separately in a numeric input. Fractional values for numeric inputs are allowed (i.e., all of these reactions are valid: A -> B, 2C -> D, 0.3E -> 1.21 A).

Ideas

• Consider using some sort of modal. The modal should have a list of species and maybe support filtering as you type, maybe using react select?
• The second screenshot shows how we do this in music box. The code for that is here, but kind of complicatd.