allow for adding custom analyzers to mapping definition

[gusdemayo]

Allow for adding analyzers to field mappings in following format

<customSearchAnalyzers>["custom_analyzer"]</customSearchAnalyzers>

[romainruaud]

Hi @gusdemayo

this looks promising, but considering modifying this part is "high risk" (it can break mapping, change behavior of fulltext search, etc...), we need some more deep testing to ensure everything is safe, so we'll need some time internally to give it a try.

In the meantime, can you have a look to the requested changes I added in my review ?

Best regards