NIFI-15648 - Resolve SECRET property values before fetchAllowableValues and verify in working flow context

[pvillard31]

Summary

NIFI-15648 - Resolve SECRET property values before fetchAllowableValues and verify in working flow context

When a connector calls fetchAllowableValues, the working flow context's ConnectorConfigurationContext may return null for properties with PropertyType.SECRET. This occurs because at the time the working flow context is cloned and setProperties resolves secrets, the backing ParameterProvider may not yet be valid, causing ParameterProviderSecretsManager.getSecretProviders() to return an empty set. The secret resolution silently stores null, and there is no subsequent re-resolution.

This does not affect verifyConfigurationStep, which bypasses stored resolved values by accepting explicit propertyValueOverrides from the UI and creating a new context with StringLiteralValue entries.

The fix adds resolvePropertyValues() calls in StandardConnectorNode before delegating to the connector's fetchAllowableValues (both overloads) and verify methods. This re-resolves SecretReference entries against the SecretsManager at the point of need, when the ParameterProvider is expected to be valid. This mirrors the existing pattern in start(), which already calls resolvePropertyValues() on the active flow context before starting the connector.

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