Function optionalCommaSeparatedList

optionalCommaSeparatedList(): ZodOptional<
ZodEffects<ZodString, string[] | undefined, string>,
>
Zod schema for optional comma-separated string list env vars.

Like commaSeparatedList, but returns undefined when the input is empty or produces no items after trimming. The resulting field type is string[] | undefined.

Use for optional list fields where absence has semantic meaning (e.g., "use defaults" for allowed origins/hosts).

Returns ZodOptional<ZodEffects<ZodString, string[] | undefined, string>>
Zod schema that outputs string[] | undefined
Example
```
// In env schema:
MCP_ALLOWED_ORIGINS: optionalCommaSeparatedList(),
MCP_ALLOWED_HOSTS: optionalCommaSeparatedList(),
```
- Defined in src/utils/zod-helpers.ts:92