Fix PaginationToken Circe codecs

[pomadchin]

Overview

This PR fixes PaginationToken circe codecs. Without it post requests with the passed next token doesn't work. I discovered this issue in terms of stac-utils/stac4s#327

Checklist

• New tests have been added or existing tests have been modified

[jisantuc]

Could this get a test? I think it wouldn't be too tough to add similar to here --

https://github.com/azavea/franklin/blob/master/application/src/test/scala/com/azavea/franklin/api/services/SearchServiceSpec.scala#L73-L82

The testing procedure would be like:

• generate two items
• send a POST search request with no filters with a limit of 1
• ensure that you can use the next link to send another valid POST request

[pomadchin]

@jisantuc ok, will push it, but I want to admit, that because codecs are incorrect test would work anyway. That's due to the fact that both default encoder and decoder are incorrect (they encode PaginationToken into a JSON object not into a string).

[pomadchin]

That's a pretty important comment

[jisantuc]

both default encoder and decoder are incorrect (they encode PaginationToken into a JSON object not into a string).

I don't think that's quite right unless you're talking about the circe codecs. The codec for the query param decodes from a b64 encoded string --

franklin/application/src/main/scala/com/azavea/franklin/api/schemas/package.scala

Lines 85 to 86 in c67f290

	implicit val codecPaginationToken: Codec.PlainCodec[PaginationToken] =
	Codec.string.mapDecode(PaginationToken.decPaginationToken)(PaginationToken.encPaginationToken)

I think actually the derived decoders just shouldn't be there, since we never want to output / consume the JSON representation with fields and want it to stay opaque for clients. Maybe I never really understood what you were saying the problem was, but if the circe codec used the same encPaginationToken and decPaginationToken methods, I think everything would be consistent?

[pomadchin]

@jisantuc not PaginationToken was the issue, but more an incorrect decoding of the SearchFilters.

[jisantuc]

🚀 it took me a minute to understand the problem, but I've confirmed now that you get the same results with:

• posting search filters with the b64 encoded pagination token in the next field
• posting empty search filters to the url with the next qp set

I also confirmed that the POST with the b64 encoded token to the AVIRIS Franklin deployment is a 400