Bad handlebars templates should not throw uncaught exceptions

[Mahoney]

Proposal

We shouldn't get stacktraces in the logs when configuring a gRPC stub with malformed handlebars - at the moment we get this:

com.google.common.util.concurrent.UncheckedExecutionException: com.github.jknack.handlebars.HandlebarsException: inline@444f0c5:16:3: found: 'assign', expected: 'parseJson'
{{/assign}}
   ^

	at com.google.common.cache.LocalCache$Segment.get(LocalCache.java:2086)
	at com.google.common.cache.LocalCache.get(LocalCache.java:4017)
	at com.google.common.cache.LocalCache$LocalManualCache.get(LocalCache.java:4898)
	at com.github.tomakehurst.wiremock.extension.responsetemplating.TemplateEngine.getTemplate(TemplateEngine.java:123)
	at com.github.tomakehurst.wiremock.extension.responsetemplating.LazyTemplateEngine.getTemplate(LazyTemplateEngine.java:32)
	at com.github.tomakehurst.wiremock.extension.responsetemplating.ResponseTemplateTransformer.transform(ResponseTemplateTransformer.java:83)
	at com.github.tomakehurst.wiremock.stubbing.AbstractStubMappings.applyV2Transformations(AbstractStubMappings.java:152)
	at com.github.tomakehurst.wiremock.stubbing.AbstractStubMappings.applyV2Transformations(AbstractStubMappings.java:155)
	at com.github.tomakehurst.wiremock.stubbing.AbstractStubMappings.applyV2Transformations(AbstractStubMappings.java:155)
	at com.github.tomakehurst.wiremock.stubbing.AbstractStubMappings.serveFor(AbstractStubMappings.java:110)
	at com.github.tomakehurst.wiremock.core.WireMockApp.serveStubFor(WireMockApp.java:293)
	at com.github.tomakehurst.wiremock.http.StubRequestHandler.handleRequest(StubRequestHandler.java:73)
	at com.github.tomakehurst.wiremock.http.AbstractRequestHandler.handle(AbstractRequestHandler.java:66)
	at org.wiremock.grpc.internal.UnaryServerCallHandler.invoke(UnaryServerCallHandler.java:57)
	at org.wiremock.grpc.internal.UnaryServerCallHandler.invoke(UnaryServerCallHandler.java:33)
	...
Caused by: com.github.jknack.handlebars.HandlebarsException: inline@444f0c5:16:3: found: 'assign', expected: 'parseJson'
{{/assign}}
   ^

	at com.github.jknack.handlebars.internal.HbsErrorReporter.syntaxError(HbsErrorReporter.java:93)
	at com.github.jknack.handlebars.internal.HbsParserFactory$1$1.reportError(HbsParserFactory.java:109)
	...
	at com.github.jknack.handlebars.Handlebars.compileInline(Handlebars.java:515)
	at com.github.tomakehurst.wiremock.extension.responsetemplating.HandlebarsOptimizedTemplate.uncheckedCompileTemplate(HandlebarsOptimizedTemplate.java:57)
	at com.github.tomakehurst.wiremock.extension.responsetemplating.HandlebarsOptimizedTemplate.<init>(HandlebarsOptimizedTemplate.java:52)
	at com.github.tomakehurst.wiremock.extension.responsetemplating.TemplateEngine.lambda$getTemplate$0(TemplateEngine.java:123)
	... 26 common frames omitted

Reproduction steps

Create a stub with broken handlbars.

References

No response