Upload a Blob Using P_Parm_Values in Pl/Sql Apex_Web_Service. Make_Rest_Request

I am trying to use Apex (cloud) to run a PL/SQL script that fetches a BLOB object from a table and sends it via a POST API call to an Alfresco Server.

If I were using Postman/Insomnia for the API call, I would do the following:

1. Set the Content-Type to be "multipart/form-data"
2. Add a key in the body called "filedata"
3. For its value, I would select a file from the local filesystem

This I would send as a POST request with basic authentication.

I am having trouble replicating this using PL/SQL with the APEX_WEB_SERVICE module. Below is the code that I am trying:

DECLARE
    f_attachment BLOB;
    f_response CLOB;
    v_login VARCHAR2(100);
    v_password VARCHAR2(100);
    l_offset     INT := 1;
    p_clob CLOB;
BEGIN
    v_login := '***';
    v_password := '***';
    
    
    
    SELECT PDF INTO f_attachment FROM VIPUL_TEST WHERE ID=2;
    
    
    apex_web_service.g_request_headers.delete;
    apex_web_service.g_request_headers(1).name := 'Content-Type';
    apex_web_service.g_request_headers(1).value := 'multipart/form-data';
    
    f_response := apex_web_service.make_rest_request(p_url => '  
                                                     p_http_method => 'POST',
                                                     p_username => v_login,
                                                     p_password => v_password,
                                                     p_parm_name => apex_util.string_to_table('filedata'),
                                                     p_parm_value => apex_util.string_to_table(apex_web_service.blob2clobbase64(f_attachment))

    );
    
    

    -- Print out the CLOB fetched from Database
    p_clob := apex_web_service.blob2clobbase64(f_attachment);

    dbms_output.put_line('Print CLOB');    
    loop  
        exit when l_offset > dbms_lob.getlength(p_clob);  
        dbms_output.put_line( dbms_lob.substr( p_clob, 255, l_offset ) );  
        l_offset := l_offset + 255;  
    end loop; 
    -- Finish Printing
END;

I am getting the below error:

ORA-06502: PL/SQL: numeric or value error
ORA-06512: at line 21
ORA-06512: at "SYS.DBMS_SQL", line 1721


1. DECLARE
2.  f_attachment BLOB;
3.  f_response CLOB;
4.  v_login VARCHAR2(100);

It seems that the clob can't be passed as a value in p_parm_value. Can you suggest a way to make this work? Is there a way to turn a Blob or a Clob into a string? I am reluctant to convert this into a varchar type, because that has an upper limit of 32kb (right?), whereas these attachments can be multiple gigabytes in size.