unable to add "literal" header values on template

I am trying to use a feign.RequestInterceptor to add headers on the fly, these headers values are simple json. Example :

public void apply(RequestTemplate template) {
  template.header("dummy", "{\"A\":{\"B\":\"C\"}}");
}

With version 10.7.4 I have got :

java.util.regex.PatternSyntaxException: Illegal repetition
{"B"

	at java.base/java.util.regex.Pattern.error(Pattern.java:2015)
	at java.base/java.util.regex.Pattern.closure(Pattern.java:3308)
	at java.base/java.util.regex.Pattern.sequence(Pattern.java:2201)
	at java.base/java.util.regex.Pattern.expr(Pattern.java:2056)
	at java.base/java.util.regex.Pattern.compile(Pattern.java:1778)
	at java.base/java.util.regex.Pattern.<init>(Pattern.java:1427)
	at java.base/java.util.regex.Pattern.compile(Pattern.java:1068)
	at feign.template.Expression.lambda$new$0(Expression.java:35)
	at java.base/java.util.Optional.ifPresent(Optional.java:183)
	at feign.template.Expression.<init>(Expression.java:35)
	at feign.template.Expressions$SimpleExpression.<init>(Expressions.java:106)
	at feign.template.Expressions.create(Expressions.java:86)
	at feign.template.Template.parseFragment(Template.java:194)
	at feign.template.Template.parseTemplate(Template.java:178)
	at feign.template.Template.<init>(Template.java:60)
	at feign.template.HeaderTemplate.<init>(HeaderTemplate.java:81)
	at feign.template.HeaderTemplate.create(HeaderTemplate.java:57)
	at feign.RequestTemplate.lambda$appendHeader$3(RequestTemplate.java:742)
	at java.base/java.util.Map.compute(Map.java:1171)
	at feign.RequestTemplate.appendHeader(RequestTemplate.java:740)
	at feign.RequestTemplate.header(RequestTemplate.java:710)
	at feign.RequestTemplate.header(RequestTemplate.java:692)

After seeing GH-1172 I had some hopes and tried with version 10.10.1, but got the same error.

I want to add "raw" headers values, no templated/parsed ones.
One simple solution would just to let this method public on RequestTemplate :

private RequestTemplate header(String name, TemplateChunk... chunks)

Start with RequestTemplate.header and the HeaderTemplate, Template, and Expression classes named in the stack trace. Reproduce the failure with a literal JSON header through RequestInterceptor, then inspect how header values are parsed. Done means literal values no longer trigger template-expression parsing and the existing behavior remains covered by tests.