Improve readability of assertion messages

[MariuszCwikla]

If there is an request processing error, e.g. syntax error:

User u = gql.document("{user(login: \"john\"){{ login status} }")
	.execute()
	.path("user")
	.entity(User.class)
	.get();
assertEquals("john", u.getLogin());

then assertion error message does not have good enough information which makes development bit harder ($Error@5bb0122])

[ERROR]   GraphQlTests.testGetUser:26 Response has 1 unexpected error(s) of 1 total. If expected, please filter them out: [org.springframework.graphql.support.DefaultExecutionGraphQlResponse$Error@5bb0122]
Request: document='{user(login: "john"){{ login status} }'

I am proposing a simple change to improve the readability. Here is the result:

[ERROR] Failures:
[ERROR]   GraphQlTests.testGetUser:34 Response has 1 unexpected error(s) of 1 total. If expected, please filter them out: [InvalidSyntaxError{ message=Invalid Syntax : offending token '{' at line 1 column 22 ,offendingToken={ ,locations=[SourceLocation{line=1, column=22}] ,sourcePreview={user(login: "john"){{ login status} }
}]
Request: document='{user(login: "john"){{ login status} }'

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