Json HTTP PATCH: Problem parsing simple leaf value

Yang model as below:
container configuration{
container system{
leaf host-name {
description "Hostname for this router";
type string

{ length "1 .. 255"; junos:posix-pattern "^[[:alnum:]._-]+$"; junos:pattern-message "Must be a string of alphanumericals, dashes or underscores"; }

}
}
}

When I tried to replace the "host-name" with following request:
PATCH http://localhost:8181/restconf/config/network-topology:network-topology/topology/topology-netconf/node/jMX/yang-ext:mount/configuration:configuration/
Payload:
{
"ietf-yang-patch:yang-patch": {
"patch-id": "ch-hn-1",
"comment": "Change Hostname-1",
"edit": [
{
"edit-id": "1",
"operation": "replace",
"target": "/configuration:system/configuration:host-name",
"value":

{ "host-name":"abc" }

}
]
}
}

The respond returns an error "Error parsing json input: Expected BEGIN_OBJECT but was STRING at line 11 column 24 path $.ietf-yang-patch:yang-patch.edit[0].value.host-name".