[ENG-9638] add search by guid for contributors and moderators add modal (#743)

- Ticket: https://openscience.atlassian.net/browse/ENG-9638
- Feature flag: n/a

## Purpose

Some user workflows rely on using the OSF profile identifiers to locate users reliably.  This was possible previously (at least in most contributor searches), but is not any longer.

## Summary of Changes

When adding contributors, searching by user GUID should call up that user. This can be implemented across all instances of this widget/modal. Requires API change

Author: mkovalua

src/app/features/moderation/services/moderators.service.ts

@@ -85,7 +85,7 @@ export class ModeratorsService {
   }
 
   searchUsers(value: string, page = 1): Observable<PaginatedData<ModeratorAddModel[]>> {
-    const baseUrl = `${this.apiUrl}/users/?filter[full_name]=${value}&page=${page}`;
+    const baseUrl = `${this.apiUrl}/search/users/?q=${value}*&page=${page}`;
 
     return this.jsonApiService
       .get<ResponseJsonApi<UserDataJsonApi[]>>(baseUrl)

src/app/shared/services/contributors.service.ts

@@ -95,8 +95,7 @@ export class ContributorsService {
   }
 
   searchUsers(value: string, page = 1): Observable<PaginatedData<ContributorAddModel[]>> {
-    const baseUrl = `${this.apiUrl}/users/?filter[full_name]=${value}&page=${page}`;
-
+    const baseUrl = `${this.apiUrl}/search/users/?q=${value}*&page=${page}`;
     return this.jsonApiService
       .get<ResponseJsonApi<UserDataJsonApi[]>>(baseUrl)
       .pipe(map((response) => ContributorsMapper.getPaginatedUsers(response)));