Command line flag to set the sslmode for PostgreSQL (Closes: #326)

The flag name and its values match libpq's sslmode connection parameter.
The default value (prefer) will first try an SSL connection; if that
fails, it will try a non-SSL connection.

Libpq documentation: https://www.postgresql.org/docs/14/libpq-connect.html#LIBPQ-CONNECT-SSLMODE

src/drivers/pgsql/drv_pgsql.c

@@ -47,6 +47,7 @@ static sb_arg_t pgsql_drv_args[] =
   SB_OPT("pgsql-user", "PostgreSQL user", "sbtest", STRING),
   SB_OPT("pgsql-password", "PostgreSQL password", "", STRING),
   SB_OPT("pgsql-db", "PostgreSQL database name", "sbtest", STRING),
+  SB_OPT("pgsql-sslmode", "PostgreSQL SSL mode (disable, allow, prefer, require, verify-ca, verify-full)", "prefer", STRING),
 
   SB_OPT_END
 };
@@ -180,7 +181,15 @@ int pgsql_drv_init(void)
   args.port = sb_get_value_string("pgsql-port");
   args.user = sb_get_value_string("pgsql-user");
   args.password = sb_get_value_string("pgsql-password");
-  args.db = sb_get_value_string("pgsql-db");
+
+  char * dbname = sb_get_value_string("pgsql-db");
+  char * sslmode = sb_get_value_string("pgsql-sslmode");
+
+  args.db = malloc(strlen("dbname= sslmode=") +
+                   strlen(dbname) +
+                   strlen(sslmode) +
+                   1);
+  sprintf(args.db, "dbname=%s sslmode=%s", dbname, sslmode);
 
   use_ps = 0;
   pgsql_drv_caps.prepared_statements = 1;

tests/t/help_drv_pgsql.t

@@ -12,4 +12,5 @@ Skip test if the PostgreSQL driver is not available.
     --pgsql-user=STRING     PostgreSQL user [sbtest]
     --pgsql-password=STRING PostgreSQL password []
     --pgsql-db=STRING       PostgreSQL database name [sbtest]
-
+    --pgsql-sslmode=STRING  PostgreSQL SSL mode (disable, allow, prefer, require, verify-ca, verify-full) [prefer]
+