Investigate using OptionSet

[glennrfisher]

An OptionSet (or something akin to [AlchemyLanguage.Options]) may be a useful way for users to declare various options without having an exhaustive set of arguments.

For example, instead of:

public func getRankedNamedEntities(
    forURL url: String,
    knowledgeGraph: QueryParam? = nil,
    disambiguateEntities: QueryParam? = nil,
    linkedData: QueryParam? = nil,
    coreference: QueryParam? = nil,
    sentiment: QueryParam? = nil,
    quotations: QueryParam? = nil,
    structuredEntities: QueryParam? = nil,
    failure: (NSError -> Void)? = nil,
    success: Entities -> Void)
{
    // ...
}

This could instead be expressed as:

public func getRankedNamedEntities(
    forURL url: String,
    options: [Options],
    failure: (NSError -> Void)? = nil,
    success: Entities -> Void)
{
    // ...
}

Which could be called as such:

alchemyLanguage.getRankedNamedEntities(
    forURL: "...",
    options: [
        .knowledgeGraph(true),
        .coreference(false),
        ...
    ]
)

[glennrfisher]

Hmm... this might not work well if only a single AlchemyLanguage.Options enum was defined. Some options are only valid for particular functions (e.g. knowledgeGraph is an acceptable parameter in many of the endpoints, but coreference is not). With only a single enum, that couldn't be expressed in code and checked by the compiler.