Make resolution priority configurable

[rstagi]

Right now the resolution priority is Override > Env > Secret File > Config File > Initial Values > Default

We should let users chose a different order by programmatically expose a stepped resolution, by splitting each resolution:

const configSchema = schema({ ...someSchema });

const config = configSchema
  .loadValues({ ...initialValues })
  .loadEnv()
  .loadConfig({ configPath })
  .override({ ...overrideValues })
  .loadSecrets()
  .validate();
// in this case secrets > override > configFile > env > initialValues > default

Also we should let this order to be configured in the bootstrap with something like:

const service = bootstrap(configSchema, {
  resolve: (configSchema) => {
    // ...custom resolution...
  },
  ...otherOptions,
},
(config) => {
  // ...factory function...
});

[rstagi]

Other possible solution, let the use choose on a single field lavel:

const configSchema = schema({
  someField: field({
    type: z.string(),
    sources: [
      secretFile("some-field"),
      valueFromConfigFile(),
      env("SOME_FIELD"),
      // resolution priority: secret > configFile > env
    ],
  }),
});