JBoss EAP 8.1 fails to start with "WFLYCTL0085: Failed to parse configuration" and "IJ010061" Unexpected element: user-name" after manually configuring datasource credentials

Issue

When manually editing the JBoss EAP 8.1 configuration file to specify the user-name and password for a datasource using the same format as previous versions, the JBoss EAP 8.1 server fails to start.

The configuration used is:

<security>
    <user-name>db-user</user-name>
    <password>db-password</password>
</security>

This results in an EAP 8.1 startup failure with the following error messages:

ERROR [org.jboss.as.server] (Controller Boot Thread) WFLYSRV0055: Caught exception during boot: org.jboss.as.controller.persistence.ConfigurationPersistenceException: WFLYCTL0085: Failed to parse configuration
    at org.jboss.as.controller@27.1.0.Final-redhat-00010//org.jboss.as.controller.persistence.XmlConfigurationPersister.load(XmlConfigurationPersister.java:123)
    at org.jboss.as.server@27.1.0.Final-redhat-00010//org.jboss.as.server.ServerService.boot(ServerService.java:384)
    at org.jboss.as.controller@27.1.0.Final-redhat-00010//org.jboss.as.controller.AbstractControllerService$1.run(AbstractControllerService.java:358)
    at java.base/java.lang.Thread.run(Thread.java:840)
Caused by: javax.xml.stream.XMLStreamException: org.jboss.as.connector.util.ParserException: IJ010061: Unexpected element: user-name
    at org.jboss.as.connector@8.1.0.GA-redhat-00015//org.jboss.as.connector.subsystems.datasources.DataSourcesExtension$DataSourceSubsystemParser.readElement(DataSourcesExtension.java:606)
    at org.jboss.as.connector@8.1.0.GA-redhat-00015//org.jboss.as.connector.subsystems.datasources.DataSourcesExtension$DataSourceSubsystemParser.readElement(DataSourcesExtension.java:195)
    at org.jboss.staxmapper@1.5.0.Final-redhat-00001//org.jboss.staxmapper.XMLMapperImpl.processNested(XMLMapperImpl.java:118)
    at org.jboss.staxmapper@1.5.0.Final-redhat-00001//org.jboss.staxmapper.XMLExtendedStreamReaderImpl.handleAny(XMLExtendedStreamReaderImpl.java:65)
    at org.jboss.as.server@27.1.0.Final-redhat-00010//org.jboss.as.server.parsing.StandaloneXml_20.parseServerProfile(StandaloneXml_20.java:680)
    at org.jboss.as.server@27.1.0.Final-redhat-00010//org.jboss.as.server.parsing.StandaloneXml_20.readServerElement(StandaloneXml_20.java:222)
    at org.jboss.as.server@27.1.0.Final-redhat-00010//org.jboss.as.server.parsing.StandaloneXml_20.readElement(StandaloneXml_20.java:134)
    at org.jboss.as.server@27.1.0.Final-redhat-00010//org.jboss.as.server.parsing.StandaloneXml.readElement(StandaloneXml.java:118)
    at org.jboss.as.controller@27.1.0.Final-redhat-00010//org.jboss.as.controller.parsing.ManagementSchema.readElement(ManagementSchema.java:53)
    at org.jboss.as.controller@27.1.0.Final-redhat-00010//org.jboss.as.controller.parsing.ManagementSchema.readElement(ManagementSchema.java:28)
    at org.jboss.staxmapper@1.5.0.Final-redhat-00001//org.jboss.staxmapper.XMLMapperImpl.processNested(XMLMapperImpl.java:118)
    at org.jboss.staxmapper@1.5.0.Final-redhat-00001//org.jboss.staxmapper.XMLMapperImpl.parseDocument(XMLMapperImpl.java:72)
    at org.jboss.as.controller@27.1.0.Final-redhat-00010//org.jboss.as.controller.persistence.XmlConfigurationPersister.load(XmlConfigurationPersister.java:112)
    ... 3 more
Caused by: org.jboss.as.connector.util.ParserException: IJ010061: Unexpected element: user-name
    at org.jboss.as.connector@8.1.0.GA-redhat-00015//org.jboss.as.connector.subsystems.datasources.DsParser.parseDsSecurity_7_1(DsParser.java:1657)
    at org.jboss.as.connector@8.1.0.GA-redhat-00015//org.jboss.as.connector.subsystems.datasources.DsParser.parseDataSource_7_0(DsParser.java:2518)
    at org.jboss.as.connector@8.1.0.GA-redhat-00015//org.jboss.as.connector.subsystems.datasources.DsParser.parseDataSources(DsParser.java:218)
    at org.jboss.as.connector@8.1.0.GA-redhat-00015//org.jboss.as.connector.subsystems.datasources.DsParser.parse(DsParser.java:175)
    at org.jboss.as.connector@8.1.0.GA-redhat-00015//org.jboss.as.connector.subsystems.datasources.DataSourcesExtension$DataSourceSubsystemParser.readElement(DataSourcesExtension.java:599)
    ... 15 more

FATAL [org.jboss.as.server] (Controller Boot Thread) WFLYSRV0056: Server boot has failed in an unrecoverable manner; exiting. See previous messages for details. - Server configuration file in use: standalone.xml

The "JBoss EAP 8.1 Configuration Guide - 11.15. Example Datasource" appears to show the same format as the previous versions, which adds to the confusion.