fix(jpa): make advanced JDBC options not log warnings IQSS#7980

With the addition of the advanced (but proprietary, Payara-only) settings
for database connection monitoring, the non-present default for connection
validation triggered unnecessary log clutter. Adding an empty default
makes these go away and is inline with the default of Payara.

doc/sphinx-guides/source/installation/config.rst

@@ -327,13 +327,13 @@ Connection Validation
    * - dataverse.db.connection-validation-method
      - | The method of connection validation:
        | ``table|autocommit|meta-data|custom-validation``
-     - *No default*
+     - *Empty string*
    * - dataverse.db.validation-table-name
      - The name of the table used for validation if the validation method is set to ``table``
-     - *No default*
+     - *Empty string*
    * - dataverse.db.validation-classname
      - The name of the custom class used for validation if the ``validation-method`` is set to ``custom-validation``
-     - *No default*
+     - *Empty string*
    * - dataverse.db.validate-atmost-once-period-in-seconds
      - Specifies the time interval in seconds between successive requests to validate a connection at most once.
      - ``0`` (disabled)

src/main/java/edu/harvard/iq/dataverse/util/DataSourceProducer.java

@@ -44,9 +44,9 @@
             // https://docs.payara.fish/community/docs/documentation/payara-server/jdbc/advanced-connection-pool-properties.html
             // VALIDATION
             "fish.payara.is-connection-validation-required=${MPCONFIG=dataverse.db.is-connection-validation-required:false}",
-            "fish.payara.connection-validation-method=${MPCONFIG=dataverse.db.connection-validation-method}",
-            "fish.payara.validation-table-name=${MPCONFIG=dataverse.db.validation-table-name}",
-            "fish.payara.validation-classname=${MPCONFIG=dataverse.db.validation-classname}",
+            "fish.payara.connection-validation-method=${MPCONFIG=dataverse.db.connection-validation-method:}",
+            "fish.payara.validation-table-name=${MPCONFIG=dataverse.db.validation-table-name:}",
+            "fish.payara.validation-classname=${MPCONFIG=dataverse.db.validation-classname:}",
             "fish.payara.validate-atmost-once-period-in-seconds=${MPCONFIG=dataverse.db.validate-atmost-once-period-in-seconds:0}",
             // LEAK DETECTION
             "fish.payara.connection-leak-timeout-in-seconds=${MPCONFIG=dataverse.db.connection-leak-timeout-in-seconds:0}",