fix: omitted $ref parameters

[markandrus]

I noticed there are some cases where parameters using $ref were omitted. This happens due to deleting the in property from the parameter, which then means, if the parameter is shared, it not longer has an in property, and is excluded from subsequent codegen steps. To fix that, I copy param in writeParameter.

Before this fix

const schema = {
  '/foo1': {
    GET: {
      args: T.Optional(
        T.Object({
          query: T.Optional(
            T.Object({
              bar: T.Optional(T.String({ 'x-in': 'query' }))
            })
          )
        })
      ),
      data: T.Any({ 'x-status-code': '201' }),
      error: T.Union([T.Any({ 'x-status-code': 'default' })])
    }
  },
  '/foo2': {
    GET: {
      args: T.Void(),
      data: T.Any({ 'x-status-code': '201' }),
      error: T.Union([T.Any({ 'x-status-code': 'default' })])
    }
  }
}

After this fix

const schema = {
  '/foo1': {
    GET: {
      args: T.Optional(
        T.Object({
          query: T.Optional(
            T.Object({
              bar: T.Optional(T.String({ 'x-in': 'query' }))
            })
          )
        })
      ),
      data: T.Any({ 'x-status-code': '201' }),
      error: T.Union([T.Any({ 'x-status-code': 'default' })])
    }
  },
  '/foo2': {
    GET: {
      args: T.Optional(
        T.Object({
          query: T.Optional(
            T.Object({
              bar: T.Optional(T.String({ 'x-in': 'query' }))
            })
          )
        })
      ),
      data: T.Any({ 'x-status-code': '201' }),
      error: T.Union([T.Any({ 'x-status-code': 'default' })])
    }
  }
}