fix(ldap-select): Filter ldap dropdown entries with search text

[ccailly]

Checklist before requesting a review

Please delete options that are not relevant.

• I have performed a self-review of my code.
• I have added tests (when available) that prove my fix is effective or that my feature works.

Description

• It fixes Dynamic filtering in LDAP question #9

This pull request improves how the searchText parameter is handled in the LDAP dropdown functionality and adds corresponding tests to ensure correct behavior. The main changes involve reading the correct request parameter and verifying expected outcomes through new test cases.

Improvements to request parameter handling:

• The LdapDropdownController now correctly reads the searchText parameter from the request, defaulting to an empty string if not provided.

Enhancements to test coverage:

• Added testSearchTextParameter to verify that providing a searchText value returns the expected filtered results in the response.
• Added testEmptySearchTextParameter to ensure that an empty searchText returns the expected number of results.