Dovecot 2.1.17 and Solr 6.6.1

[Siarhei Chystsiakou]

Hello.
I'm trying to set fts plugin for working with Apache Solr 6.6.1, but after
the setting I get the following error ....

o.a.s.h.RequestHandlerBase org.apache.solr.common.SolrException: Bad
contentType for search handler :text/xml
request={q=from:"test"&fl=uid,score&sort=uid+asc&fq=%2Bbox:a8012d2edac165591d3c000043730d65+%2Buser:"
user at example.com"&rows=5543}

I've set everything according to the guide on the site as well as taking
into consideration such conversation in maillist in February 2017 (
https://dovecot.org/list/dovecot/2017-February/107255.html).

The current dovecot configuration:...

#cat /etc/dovecot/conf.d/90-fts.conf
plugin {
    fts = solr
    fts_solr = debug break-imap-search url=
http://127.0.0.1:8983/solr/dovecot/
}

full config the dovecot: https://hastebin.com/awuwohanoz.makefile

I also enclose the screen from wireshark https://itmag.es/6mWng

Thanks!