[QOS][SOLANA] Add Solana Epoch Check

[fredteumer]

Objective

Create a QoS Check that ensures Solana nodes adhere to the 6 epoch historical requirement.

Origin Document

The Pocket Morse service describes this as a requirement for Solana.

While providing Solana Archival support is infeasible, our customers would like as much historical data as possible. While searching for a nexus-point of cost effectiveness to historical data, we chose to move forward with "Solana Custom" which supports the current epoch plus the 6 most recent epochs.

Goals

• Create a QoS check that ensures all Solana nodes have 6 epochs of data available.

Deliverables

• A QoS check that can successfully filter out nodes that do not provide the current epoch - 6 worth of data.
• Metrics that prove that this is working as expected.

Non-goals / Non-deliverables

• Sync check for Solana
• Chain check for Solana
• Any other config checks for Solana

General deliverables

• Comments: Add/update TODOs and comments alongside the source code so it is easier to follow.
• Testing: Add new tests (unit and/or E2E) to the test suite.
• Makefile: Add new targets to the Makefile to make the new functionality easier to use.
• Documentation: Update architectural or development READMEs; use mermaid diagrams where appropriate.

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Creator: [GitHub handle of issue owner]
Co-Owners: [OPTIONAL - GitHub handle of co-owner(s)]

[fredteumer]

For the Epoch check:

Recommended Method

• Get the currentEpoch using getEpochInfo
• Fetch the Epoch schedule with getEpochSchedule
• Get a random slot from currentEpoch - 7

start_slot = firstNormalSlot + (target_epoch - firstNormalEpoch) * slotsPerEpoch
end_slot = start_slot + slotsPerEpoch - 1

• Get the block details of a random slot between start_slot and end_slot with getBlock
• Ensure a valid response is returned (or check some consistent smart contract)

Naive Method

• use getFirstAvailableBlock to determine the first available block on the node
• Get the currentEpoch using getEpochInfo
• Fetch the Epoch schedule with getEpochSchedule
• Ensure parentSlot is within an acceptable range of currentSlot - (7 * slotsPerEpoch)

please feel free to check my actual implementation details, but I believe the methodology is sound.