Prior to this commit, the PropertyResolver API (and therefore the
Environment API) allowed callers a choice between
#resolvePlaceholders and #resolveRequiredPlaceholders for low-level
${placeholder} resolution. However, when calling the higher level
#getProperty variants, users had no control over whether property
values returned with unresolvable ${placeholders} would result in an
exception or simply be passed through.
This commit introduces a #setIgnoreUnresolvableNestedPlaceholders
property via ConfigurablePropertyResolver, defaulting to false, the
value of which is respected by AbstractPropertyResolver#getProperty
method implementations. See the new test in
PropertySourcesPropertyResolverTests for usage examples.
Issue: SPR-9569, SPR-9473
06e34f05a6