Many JDBCConnectionExceptions are thrown when muse is under heavy load

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Details:
- It looks like muse is unsuccessfully attempting to get JDBC connections for transactionals (see logs observed during heavy submission load bellow)
- JDBC connections is used for flyway but the data operation should be via R2DBC connections
- Most likely there is a mismatch between db drivers injection some where (or could be something else)
- the overload of exceptions eventually makes muse unhealthy and it gets restarted (which is bad if we have inflight submissions as they are lost)

Logs while muse was running during some submissions:


Expected Behavior:
- muse should be consistent with its db connections

Start by reproducing the JDBC connection exceptions during heavy submission load and trace which transactional operations request JDBC connections instead of R2DBC connections. Use the reported logs as the initial symptom; done means database operations use the intended connection type and Muse remains healthy without losing inflight submissions.

Written by the indexing model from the issue text.