Template Tag Function Editor (#67)

![CleanShot 2024-08-15 at 16 53
09@2x](https://github.com/user-attachments/assets/8c0eb655-1daf-4dc8-811f-f606c770f7dc)

src-web/hooks/useTemplateFunctions.ts

@@ -0,0 +1,88 @@
+import type { HttpRequest } from '@yaakapp/api';
+
+export interface TemplateFunctionArgBase {
+  name: string;
+  optional?: boolean;
+  label?: string;
+}
+
+export interface TemplateFunctionSelectArg extends TemplateFunctionArgBase {
+  type: 'select';
+  defaultValue?: string;
+  options: readonly { name: string; value: string }[];
+}
+
+export interface TemplateFunctionTextArg extends TemplateFunctionArgBase {
+  type: 'text';
+  defaultValue?: string;
+  placeholder?: string;
+}
+
+export interface TemplateFunctionHttpRequestArg extends TemplateFunctionArgBase {
+  type: HttpRequest['model'];
+}
+
+export type TemplateFunctionArg =
+  | TemplateFunctionSelectArg
+  | TemplateFunctionTextArg
+  | TemplateFunctionHttpRequestArg;
+
+export interface TemplateFunction {
+  name: string;
+  args: TemplateFunctionArg[];
+}
+
+export function useTemplateFunctions() {
+  const fns: TemplateFunction[] = [
+    {
+      name: 'timestamp',
+      args: [
+        {
+          type: 'text',
+          name: 'from',
+          label: 'From',
+          placeholder: '2023-23-12T04:03:03',
+          optional: true,
+        },
+        {
+          type: 'select',
+          label: 'Format',
+          name: 'format',
+          options: [
+            { name: 'RFC3339', value: 'rfc3339' },
+            { name: 'Unix', value: 'unix' },
+            { name: 'Unix (ms)', value: 'unix_millis' },
+          ],
+          optional: true,
+          defaultValue: 'RFC3339',
+        },
+      ],
+    },
+    {
+      name: 'response',
+      args: [
+        {
+          type: 'http_request',
+          name: 'request',
+          label: 'Request',
+        },
+        {
+          type: 'select',
+          name: 'attribute',
+          label: 'Attribute',
+          options: [
+            { name: 'Body', value: 'body' },
+            { name: 'Header', value: 'header' },
+          ],
+        },
+        {
+          type: 'text',
+          name: 'filter',
+          label: 'Filter',
+          placeholder: 'JSONPath or XPath expression',
+        },
+      ],
+    },
+  ];
+  return fns;
+}