//Find and store the attachment names in a paragrahp custom field 
def issueKey = 'NOT-1'

def result = get('/rest/api/2/issue/' + issueKey)
        .header('Content-Type', 'application/json')
        .asObject(Map)
        
        
def filenames = result.body.fields.attachment.filename.join(", ")

        
def result2 = put('/rest/api/2/issue/' + issueKey)
        .header('Content-Type', 'application/json')
        .body([
        fields:[
                customfield_10079: filenames
        ]
])
        .asString()  
        
        
if (result2.status >= 200 && result2.status<300){
    return filenames
} else {
   return "Failed to update custom field with the attachment names"
}