Pass 1 of pulling traefik config into functions

server/lib/traefik/headersMiddleware.ts

@@ -0,0 +1,46 @@
+import logger from "@server/logger";
+
+/**
+ * Build the customRequestHeaders middleware definition for a resource's
+ * custom headers + setHostHeader config. Returns null when there are no
+ * headers to set, so the caller can skip attaching the middleware.
+ */
+export function buildCustomHeadersMiddleware(
+    headers: string | null | undefined,
+    setHostHeader: string | null | undefined,
+    resourceId: number
+): { headers: { customRequestHeaders: { [key: string]: string } } } | null {
+    const headersObj: { [key: string]: string } = {};
+
+    if (headers) {
+        let headersArr: { name: string; value: string }[] = [];
+        try {
+            headersArr = JSON.parse(headers) as {
+                name: string;
+                value: string;
+            }[];
+        } catch (e) {
+            logger.warn(
+                `Failed to parse headers for resource ${resourceId}: ${e}`
+            );
+        }
+
+        headersArr.forEach((header) => {
+            headersObj[header.name] = header.value;
+        });
+    }
+
+    if (setHostHeader) {
+        headersObj["Host"] = setHostHeader;
+    }
+
+    if (Object.keys(headersObj).length === 0) {
+        return null;
+    }
+
+    return {
+        headers: {
+            customRequestHeaders: headersObj
+        }
+    };
+}