Clarify the comma in "spring.config.activate.on-profile" value and add test

[quaff]

See spring-cloud/spring-cloud-commons#1416 (comment)

[wilkinsona]

Thanks for the suggestion but I think this may cause confusion. , isn't really the equivalent of |. It's a separator for the expressions when configured as a single comma-separate value due to it being bound to a String[]. If it's configured as a list, no separation occurs. In other words, the following two snippets of YAML are not equivalent:

spring.config.activate.on-profile:
    - a|b

spring.config.activate.on-profile:
    - a,b

I think it would be better to update the table in this section of the documentation to describe on-profile more accurately. Perhaps something like "profile expressions of which at least one must match for the document to be active".

[quaff]

Updated, could someone review the wording?