Support deprecated delimited_payload_filter name in deserialization (#…

…3835)

Relates: elastic/elasticsearch#27705

This commit adds support for the deprecated delimited_payload_filter
name when deserializing token filters in a 6.x index within a 7.x cluster.

When serializing, the new name delimited_payload will be used.

src/Nest/Analysis/TokenFilters/TokenFilterFormatter.cs

@@ -16,6 +16,7 @@ internal class TokenFilterFormatter : IJsonFormatter<ITokenFilter>
 			{ "asciifolding", 0 },
 			{ "common_grams", 1 },
 			{ "delimited_payload", 2 },
+			{ "delimited_payload_filter", 2 },
 			{ "dictionary_decompounder", 3 },
 			{ "edge_ngram", 4 },
 			{ "elision", 5 },