Fix serialization issue

[lassemand]

Purpose

❯ kubectl logs ccdscan-indexer-959cb5855-j687w --previous
2024-12-04T10:27:02.227910Z  INFO ccdscan_indexer: Metrics server is running at 0.0.0.0:13030
2024-12-04T10:27:02.228934Z  INFO concordium_scan::indexer: Indexing from block height 90777
2024-12-04T10:27:02.246321Z  INFO concordium_scan::indexer: Connection established to node at uri: https://reporters.internal.stagenet.concordium.com:20000/
2024-12-04T10:27:02.327368Z ERROR ccd_event_processor: Failed to process event: error returned from database: unsupported Unicode escape sequence. Took 66ms to fail.
2024-12-04T10:27:02.327383Z  INFO ccd_event_processor: Retrying in 5000ms.
2024-12-04T10:27:07.328284Z  INFO concordium_scan::indexer: Failed processing 1 times in row: error returned from database: unsupported Unicode escape sequence

Underlying reason is that we serialise decoded data when using Cbor in the indexer.

Changes

Change decoding from indexer to api

Checklist

• My code follows the style of this project.
• The code compiles without warnings.
• I have performed a self-review of the changes.
• I have documented my code, in particular the intent of the
  hard-to-understand areas.
• (If necessary) I have updated the CHANGELOG.