Generate Dovecot dh params locally until release 2.3

dovecot/conf/dovecot.conf

@@ -58,7 +58,10 @@ namespace inbox {
 ssl = yes
 ssl_cert = </certs/cert.pem
 ssl_key = </certs/key.pem
-ssl_dh = </certs/dhparam.pem
+# This will be enabled once 2.3 is released
+# ssl_dh = </certs/dhparam.pem
+# In the meanwhile:
+ssl_dh_parameters_length = 2048
 # TLS hardening is based on the following documentation:
 # https://bettercrypto.org/static/applied-crypto-hardening.pdf
 ssl_protocols=!SSLv3 !SSLv2