Use a single memoryLimit instead of memory and memorySwap

We will make the percent allocation dynamic depending on the system.

When we have servers with a large amount of RAM but little swap, we
seem to use a lot of swap because of 50% allocation strategy. In such
systems, we run out of swap and thus have OOM errors even though there
is a lot of RAM available!

migrations/20210120025243-settings-platform-config-memoryLimit.js

@@ -0,0 +1,23 @@
+'use strict';
+
+exports.up = function(db, callback) {
+    db.all('SELECT * FROM settings WHERE name=?', ['platform_config'], function (error, results) {
+        if (error || results.length === 0) return callback(null);
+
+        let value = JSON.parse(results[0].value);
+
+        for (const serviceName of Object.keys(value)) {
+            const service = value[serviceName];
+            if (!service.memorySwap) continue;
+            service.memoryLimit = service.memorySwap;
+            delete service.memorySwap;
+            delete service.memory;
+        }
+
+        db.runSql('UPDATE settings SET value=? WHERE name=?', [ JSON.stringify(value), 'platform_config' ], callback);
+    });
+};
+
+exports.down = function(db, callback) {
+    callback();
+};