Implement info.put() database method.

Replaces an existing element with a new one, or inserts it
if there is nothing to replace. The element may be deeply
nested inside a JSON object or array in the `info` table.

Works for both public.info and survey_?.info.

lib/www/server/lib/db/info/put.js

@@ -0,0 +1,37 @@
+const { setSurvey, transaction } = require('../connection');
+
+async function put (projectId, path, payload, opts = {}) {
+	const client = await setSurvey(projectId);
+	const [key, ...jsonpath] = (path||"").split("/").filter(i => i.length);
+
+	try {
+		const text = jsonpath.length
+			? `
+				INSERT INTO info (key, value)
+				VALUES ($2, jsonb_set('${isNaN(Number(jsonpath[0])) ? "{}" : "[]"}'::jsonb, $3, $1))
+				ON CONFLICT (key) DO UPDATE
+					SET
+						key = $2,
+						value = jsonb_set((SELECT value FROM info WHERE key = $2), $3, $1)
+				RETURNING *;
+			`
+			: `
+				INSERT INTO info (key, value)
+				VALUES ($2, $1)
+				ON CONFLICT (key) DO UPDATE
+					SET
+						key = $2,
+						value = $1
+				RETURNING *;
+			`;
+		const values = jsonpath.length ? [JSON.stringify(payload), key, jsonpath] : [JSON.stringify(payload), key];
+		await client.query(text, values);
+	} catch (err) {
+		console.error("ERROR", err);
+		throw err;
+	} finally {
+		client.release();
+	}
+}
+
+module.exports = put;