Resolves the headers attribute of a custom model preference entry. Since preferences are
user-authored JSON, entries with a non-string value are dropped. Returns undefined when no
usable header remains, so that the default request headers are left untouched. The keys are
sorted, so equal header maps stringify identically regardless of their order in the preference.
Resolves the
headersattribute of a custom model preference entry. Since preferences are user-authored JSON, entries with a non-string value are dropped. Returnsundefinedwhen no usable header remains, so that the default request headers are left untouched. The keys are sorted, so equal header maps stringify identically regardless of their order in the preference.