private async IAsyncEnumerable<DocumentKey> SearchDocumentsAsync(
    OrgSlug org,
    string? searchTerm,
    DocumentTypeSet documentTypes,
    bool includeUntypedDocuments,
    DocumentRelativePath? startAfter,
    [EnumeratorCancellation] CancellationToken cancellationToken)
{
    var query = searchTerm?.Trim();

    await foreach (var doc in ListDocumentsAsync(org, startAfter, cancellationToken))
    {
        if (!doc.Type.MatchesFilter(documentTypes, includeUntypedDocuments))
            continue;

        if (!String.IsNullOrEmpty(query) && !doc.Name.Matches(query))
            continue;

        yield return doc;
    }
}

// Houston/Model/Documents/DocumentName.cs
public bool Matches(string pattern)
{
    return Value.Contains(pattern, StringComparison.CurrentCultureIgnoreCase);
}

// Houston/Model/Documents/DocumentType.cs
public bool MatchesFilter(DocumentTypeSet documentTypes, bool includeUntypedDocuments)
{
    if (documentTypes.IsEmpty && !includeUntypedDocuments)
        return true;

    if (documentType is null)
        return includeUntypedDocuments;

    return documentTypes.Types.Contains(documentType.Value);
}