fix: export runtime metadata

[th7nder]

Description

Our current runtime configuration does not expose Runtime API metadata.
It's due to a 'bug' in (https://github.com/paritytech/polkadot-sdk-parachain-template), which was discovered while trying to implement an Runtime API using subxt to generate a deadline info needed for #449 .

The bug is described in paritytech/subxt#1873.
TL;DR when impl_runtime_apis! is not implemented in the root module lib.rs the trait visibility rules are broken and APIs are not exposed.

polka-storage git:(fix/no-ref/export-runtime-metadata) ✗ subxt explore -a --url http://0.0.0.0:42069          
Usage:
    subxt explore pallet <PALLET>
        explore a specific pallet
    subxt explore api <RUNTIME_API>
        explore a specific runtime api

Available <PALLET>'s are:
    Aura
    AuraExt
    Authorship
    Balances
    CollatorSelection
    CumulusXcm
    Faucet
    Market
    MessageQueue
    ParachainInfo
    ParachainSystem
    PolkadotXcm
    Proofs
    Randomness
    RandomnessSource
    Session
    StorageProvider
    Sudo
    System
    Timestamp
    TransactionPayment
    XcmpQueue

Available <RUNTIME_API>'s are:
    AccountNonceApi
    AuraApi
    AuraUnincludedSegmentApi
    BlockBuilder
    CollectCollationInfo
    Core
    GenesisBuilder
    Metadata
    OffchainWorkerApi
    SessionKeys
    TaggedTransactionQueue
    TransactionPaymentApi
    TransactionPaymentCallApi

[aidan46]

Nicely dug out, good job! You should close the subxt issue if the fix was on the parachain side.

[jmg-duarte]

Nicely dug out, good job! You should close the subxt issue if the fix was on the parachain side.

The fix is not on the parachain side, the bandaid is. This is an issue on their end, and they even discussed that they wanted to separate things because they didn't want a super large file.