Add MEMBER_ROLE to LEVEL_TYPES frontend constants
## Context
| | |
|---|---|
| **Phase** | 4 of 6 |
| **Parallel with** | https://gitlab.com/gitlab-org/gitlab/-/work_items/594885+ |
| **Blocked by** | https://gitlab.com/gitlab-org/gitlab/-/work_items/594880+ <br> https://gitlab.com/gitlab-org/gitlab/-/work_items/594881+ <br> https://gitlab.com/gitlab-org/gitlab/-/work_items/594882+ <br> https://gitlab.com/gitlab-org/gitlab/-/work_items/594883+ <br> https://gitlab.com/gitlab-org/gitlab/-/work_items/594884+ |
| **Unblocks** | https://gitlab.com/gitlab-org/gitlab/-/work_items/594887+ <br> https://gitlab.com/gitlab-org/gitlab/-/work_items/594888+ <br> https://gitlab.com/gitlab-org/gitlab/-/work_items/594889+ <br> https://gitlab.com/gitlab-org/gitlab/-/work_items/594890+ |
## Summary
Add `MEMBER_ROLE: 'member_role'` to the `LEVEL_TYPES` constant in both the project and group settings constants files so that the new type can be used consistently across frontend components.
## Background
`LEVEL_TYPES` in `app/assets/javascripts/projects/settings/constants.js` defines the string identifiers used to categorise items in the access dropdown (`role`, `user`, `group`, `deploy_key`). A parallel constant exists for groups at `app/assets/javascripts/groups/settings/constants.js`.
Adding `MEMBER_ROLE` here makes it available across all components that import from these files and ensures consistent naming.
## Changes required
### `app/assets/javascripts/projects/settings/constants.js`
```javascript
export const LEVEL_TYPES = {
ROLE: 'role',
USER: 'user',
DEPLOY_KEY: 'deploy_key',
GROUP: 'group',
MEMBER_ROLE: 'member_role',
};
```
### `app/assets/javascripts/groups/settings/constants.js`
```javascript
export const LEVEL_TYPES = { ROLE: 'role', GROUP: 'group', USER: 'user', MEMBER_ROLE: 'member_role' };
```
## Notes
- Adding `MEMBER_ROLE` to `LEVEL_TYPES` in CE is safe — the dropdown component only renders the custom roles section when `customRoles.length > 0` (which is only populated in EE). There is no risk of showing empty custom role sections in CE.
- The string value `'member_role'` must match the `type` string returned by the backend (`humanize_member_role` dispatches from `type == :member_role`), and must match the key used in `setDataForSave` to detect `member_role_id` items (Issue 14).
## Testing
- No dedicated test needed — this is a constants change. Tests in Issues 13 and 14 will validate the constant is used correctly.
## Dependencies
None — can be done immediately, in parallel with all other issues.
## Labels
issue