Observation Instrumentation will double-wrap CompletionExceptions

[osi]

spring-graphql/spring-graphql/src/main/java/org/springframework/graphql/observation/GraphQlObservationInstrumentation.java

Line 152 in 1032f99

throw new CompletionException(error);

This line will unconditionally wrap error in a CompletionException. If the incoming error is already a CompletionException, this leads to confusing double-wrapping. Consider doing what CompletableFuture does and conditionally wrapping:

    /**
     * Returns the encoding of the given (non-null) exception as a
     * wrapped CompletionException unless it is one already.
     */
    static AltResult encodeThrowable(Throwable x) {
        return new AltResult((x instanceof CompletionException) ? x :
                             new CompletionException(x));
    }