Extend HTTP integration GraphQL query to return the custom mapping params

Contributes to #262707 (closed)

The query should provide payload_example, payload_attribute_mapping, and payload_attributes (the name may be changed).

The format of payload_attribute_mapping should match the schema and match the following format:

{
	"title": { "path": ["alert", "name"], "type": "string" },
        "start_time": { "path": ["started_at"], "type": "datetime" }
}

The payload_attributes is the list of all possible attributes from the payload example. Has the following format:

[
	{ "path": ["foo", "bar"], "type": "string", "label": "Bar" },
	{ ... }
]

Where the path is a key's path in the payload. The type is "detected" type of value (We'll try to detect a date time). The label is a human-readable version of the path.