Require explicit representation configuration for UUID, BigDecimal, and BigInteger

[HyunSangHan]

Remove implicit defaults for UUID, BigDecimal, and BigInteger representations to force explicit configuration.

• MongoConfigurationSupport: Require explicit UuidRepresentation configuration in mongoClientSettings()
• MongoClientFactoryBean: Require explicit UuidRepresentation configuration in computeClientSetting()
• MongoCustomConversions: Require explicit BigDecimalRepresentation configuration (covers both BigDecimal and BigInteger)

Resolves: #5037

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[mp911de]

The way these changes manifest is that application startup always breaks if uuid/big decimal representations aren't configured. That isn't ideal as users that don't need these features are forced to make a configuration change.

It would be much more appropriate to check whether such types are used at all.

A utility that walks the MongoMappingContext and introspects whether entities have a property that uses UUID, BigDecimal, or BigInteger would be less invasive and more targeted. We clearly cannot capture uuid/big decimal usage that operates solely on Documents (no entity usage) and in these cases, applications would only fail during runtime.

[mp911de]

We would break applications for users that do not use UUIDs.

[mp911de]

Same breaking behavior as for UUIDs. We would also break applications for users that do not use big decimals.

[mp911de]

See above.