side product and byproduct

[qai222]

Is your feature request related to a problem? Please describe.
There should be a way to tell if a non-desired product is a side product or a byproduct.

We already have a univalued reaction_role field for each compound, which implies a main chemical equation (based on which reaction_roles are assigned).

• The products of this equation = one desired product + a set of byproducts.
• If a product is not on the right side of the main chemical equation, by definition it is a side product;
  • Side products are excluded in balancing the main chemical equation.

Describe the solution you'd like
extend the enum ReactionRoleType to include SIDE_PRODUCT

    // If a ProductCompound has reaction_role == PRODUCT and is_desired_product == True,
    // then it is the desired product of the main chemical equation.
    // If a ProductCompound has reaction_role == PRODUCT and is_desired_product == False,
    // then it is a byproduct product of the main chemical equation.
    // If a ProductCompound has reaction_role == SIDE_PRODUCT,
    // then it is a product not in the main chemical equation.
    SIDE_PRODUCT = 9;