DB connection: defaults and more options

[poikilotherm]

Now that #7701 is merged and we are on 5.2021.4, we can enable real defaults for the database connection.

Context

I learned that any variable expansion supporting annotations or files, that will have Payara create resources, containers or sth else from, will not retrieve default values from the microprofile-config.properties file bundled in the WAR.

Instead, we need to provide defaults with the new ${MPCONFIG=name:default} syntax.

Todo

• Add defaults to the connection URL. Using "localhost", "5432" and "dataverse" will allow most installation and devs to go without config.
• Use the newly introduced caps to configure more Payara specific properties regarding connection monitoring etc.
• Edit release notes of 5.3 to be more precise about database configuration not having defaults...
• Maybe others

[poikilotherm]

FWIW: this can now be addressed given the fact that Payara 5.2022.2 included a fix for this.