Restconf HTTPAPI plugin and modules (#49476)

* Initial code for restconf support

*  Add restconf httpapi plugin
*  Add restonf_get module

* Fix some ConnectionError usage

lib/ansible/plugins/httpapi/restconf.py

@@ -0,0 +1,79 @@
+# Copyright (c) 2018 Cisco and/or its affiliates.
+#
+# This file is part of Ansible
+#
+# Ansible is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# Ansible is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with Ansible.  If not, see <http://www.gnu.org/licenses/>.
+#
+
+from __future__ import (absolute_import, division, print_function)
+
+__metaclass__ = type
+
+DOCUMENTATION = """
+---
+author: Ansible Networking Team
+httpapi: restconf
+short_description: HttpApi Plugin for devices supporting Restconf API
+description:
+  - This HttpApi plugin provides methods to connect to Restconf API
+    endpoints.
+version_added: "2.8"
+options:
+  root_path:
+    type: str
+    description:
+      - Specifies the location of the Restconf root.
+    default: '/restconf'
+    vars:
+      - name: ansible_httpapi_restconf_root
+"""
+
+import json
+
+from ansible.module_utils.network.common.utils import to_list
+from ansible.module_utils.connection import ConnectionError
+from ansible.plugins.httpapi import HttpApiBase
+
+
+CONTENT_TYPE = 'application/yang.data+json'
+
+
+class HttpApi(HttpApiBase):
+    def send_request(self, data, **message_kwargs):
+        if data:
+            data = json.dumps(data)
+
+        path = self.get_option('root_path') + message_kwargs.get('path', '')
+
+        headers = {
+            'Content-Type': message_kwargs.get('content_type') or CONTENT_TYPE,
+            'Accept': message_kwargs.get('accept') or CONTENT_TYPE,
+        }
+        response, response_data = self.connection.send(path, data, headers=headers, method=message_kwargs.get('method'))
+
+        return handle_response(response_data.read())
+
+
+def handle_response(response):
+    if 'error' in response and 'jsonrpc' not in response:
+        error = response['error']
+
+        error_text = []
+        for data in error['data']:
+            error_text.extend(data.get('errors', []))
+        error_text = '\n'.join(error_text) or error['message']
+
+        raise ConnectionError(error_text, code=error['code'])
+
+    return response