Generate builder objects for building API objects

[wafflespeanut]

The first step to generating client code would be to build type-safe compile-time checked API objects. This is done by leveraging PhantomData and unit types. An example would be:

struct MissingName;
struct MissingNamespace;
struct NamePresent;
struct NamespacePresent;

struct Get;

#[repr(transparent)]    // for safely transmuting
#[derive(Debug, Clone)]
pub struct ConfigMapFactory<Name, Namespace> {
    inner: ConfigMapBuilder,
    _param_name: PhantomData<Name>,
    _param_namespace: PhantomData<Namespace>,
}

#[derive(Default, Debug, Clone)]
struct ConfigMapBuilder {
    inner: ConfigMap,
    name: Option<String>,
    namespace: Option<String>,
}

impl ConfigMap {
    fn get() -> ConfigMapFactory<MissingName, MissingNamespace> {
        ConfigMapFactory {
            inner: Default::default(),
            _param_name: PhantomData,
            _param_namespace: PhantomData,
        }
    }
}

impl<A> ConfigMapFactory<MissingName, A> {
    pub fn name(mut self, name: &str) -> ConfigMapFactory<NamePresent, A> {
        self.inner.name = Some(name.into());
        unsafe { mem::transmute(self) }
    }
}

Then, we'll add an impl for the actual API request only when the type has NamePresent and NamespacePresent (we do this for all required parameters and fields). This means rustc won't compile the code when the user forgets some required entity.

Anyway, the focus for this issue would be to generate all of this stuff for all API objects (taking into account of required parameters and fields).

[wafflespeanut]

I had to do some workarounds for some edge cases, for which I've dropped FIXMEs, but aside that, IT IS DONE - the generated docs are live!