feat(module): improve app config types autocomplete (#1870)

Co-authored-by: Dave Stewart <dev@davestewart.co.uk>
Co-authored-by: Benjamin Canac <canacb1@gmail.com>

src/runtime/types/utils.d.ts

@@ -1,15 +1,23 @@
 export type Strategy = 'merge' | 'override'
 
+export interface TightMap<O = any> {
+  [key: string]: TightMap | O
+}
+
+export type DeepPartial<T, O = any> = {
+  [P in keyof T]?: T[P] extends object
+    ? DeepPartial<T[P], O>
+    : T[P];
+} & {
+  [key: string]: O | TightMap<O>
+}
+
 export type NestedKeyOf<ObjectType extends Record<string, any>> = {
   [Key in keyof ObjectType]: ObjectType[Key] extends Record<string, any>
   ? NestedKeyOf<ObjectType[Key]>
   : Key
 }[keyof ObjectType]
 
-export type DeepPartial<T> = Partial<{
-  [P in keyof T]: DeepPartial<T[P]> | { [key: string]: string | object }
-}>
-
 type DeepKey<T, Keys extends string[]> =
   Keys extends [infer First, ...infer Rest]
     ? First extends keyof T