API returns incomplete results (15 max) for transfers within same block

[aslobodnik]

Describe the bug
The /api/v1/safes/{address}/transfers/ endpoint silently fails to return more than 15 transfers if those transfers occurred within a single block.

To Reproduce
Steps to reproduce the behavior:

1. GET on https://api.safe.global/tx-service/eth/api/v1/safes/0x3B59C6d0034490093460787566dc5D6cE17F2f9C/transfers/?limit=50

   • For block 23497363 there are 15 transfers.

2. GET on https://api.safe.global/tx-service/eth/api/v1/safes/0x3B59C6d0034490093460787566dc5D6cE17F2f9C/transfers/?limit=50&block_number=23497363

   • Works correctly: there are now 21 transfers for block 23497363 but required a block_number filter

Expected behavior
All 21 transfers from block 23497363 should be returned, not capped at 15.

Environment (please complete the following information):

• Staging or production? Prod
• Which chain? Ethereum Mainnet (ETH)