error not found with `application/vnd.iota.serializer-v1` header in core api

[lzpap]

Bug description

The core API route /api/core/v2/outputs/:outputId does not work with the Accept header being set to application/vnd.iota.serializer-v1, which is the only supported route in iota.go's node client implementation.

Chronicle version

The one deployed behind the public IOTA mainnet instance.

Steps to reproduce the bug

The easiest is to reproduce it with Postman, so you can directly edit the request.

1. GET request to https://chronicle.stardust-mainnet.iotaledger.net/api/core/v2/outputs/0xb191c4bc825ac6983789e50545d5ef07a1d293a98ad974fc9498cb181aa52d000000 with the Accept header being set to application/json. Works!
   
2. GET request to https://chronicle.stardust-mainnet.iotaledger.net/api/core/v2/outputs/0xb191c4bc825ac6983789e50545d5ef07a1d293a98ad974fc9498cb181aa52d000000 with the Accept header being set to application/vnd.iota.serializer-v1.
   

When I try to run the same query with the iota.go lib's client (that uses the application/vnd.iota.serializer-v1 header) I get back a similar response:

not found: url https://chronicle.stardust-mainnet.iotaledger.net/api/core/v2/outputs/0xb191c4bc825ac6983789e50545d5ef07a1d293a98ad974fc9498cb181aa52d000000, error message: 

Expected behaviour

Chronicle's node API handles requests with the application/vnd.iota.serializer-v1 accept header.

Actual behaviour

404 answer from chronicle.

[DaughterOfMars]

There appears to be no milestone data before 7669901, and this output was booked in milestone 7669900. Because of that, chronicle does not have protocol parameters available and cannot serialize the output.