dovecot - Oct 2020 - where to specify dovecot v2.3.11.3 SSL configs for fts solr indexer/backend connection?

I'm running.

	dovecot --version
		2.3.11.3 (502c39af9)

	solr -version
		8.6.3

solr's configured to use SSL.

dovecot correctly uses SSL for transport

	fts_solr = url=https://solr.example.com:8984/solr/dovecot/

adding solr-side SSL client auth,

-	SOLR_SSL_NEED_CLIENT_AUTH=false
+	SOLR_SSL_NEED_CLIENT_AUTH=need

I need to specify client cert for dovecot to present -- specific to the fts
indexer connection.

It apparently does not use dovecot's general/global SSL configs; that^
toggle immediately breaks MUA-originated search, reporting only

	2020-10-11 18:23:30 imap(myuser at example)<oKpmJW+xQKCsHgsH>: Error:
fts_solr: Lookup failed: 401 Unauthorized

All other protocols SSL configs certainly work, and can be individually
configured with specific key/crt pairs.

Where do I config dovecot specifically for the search backend?

I.e., where do I assign the ssl key/cert for dovecot to present as client to the
solr server ?