Send a PDF file to telegram using PL/SQL- UTL_HTTP code - oracle

Question

I'm trying to send a pdf document and a small description about it from my server to a Telegram group using a Telegram bot user. I'm able to send a document by itself using the method /sendDocument. However, that is not exactly what I want. I wonder is that even possible to do ?
The actual output message is "ORA-29263: HTTP protocol error."
declare
l_attachment blob;
l_newline varchar2(50) := chr(13) || chr(10);
lco_boundary constant varchar2(30) := '----=*#abc1234321cba#*=';
l_http_request utl_http.req;
l_request_body clob;
l_request_body_length number;
l_http_response utl_http.resp;
l_response_header_name varchar2(256);
l_response_header_value varchar2(1024);
l_response_body varchar2(32767);
l_offset number := 1;
l_amount number := 2000;
l_buffer varchar2(2000);
postData clob;
p_id varchar2(50) := '********';
begin
select invoce into l_attachment from some_table;
l_request_body := l_newline
|| '--' || lco_boundary || l_newline
|| 'Content-Disposition: form-data; name="document"; filename="file.pdf"' || l_newline
|| 'Content-Type: application/pdf' || l_newline
|| l_newline
|| apex_web_service.blob2clobbase64(l_attachment) || l_newline
|| '--' || lco_boundary || l_newline
|| 'Content-Disposition: form-data; name="document"' || l_newline
|| l_newline
|| 'file.pdf' || l_newline
|| '--' || lco_boundary || l_newline
|| 'Content-Disposition: form-data; name="MAX_FILE_SIZE"' || l_newline
|| l_newline
|| '4000000' || l_newline
|| '--' || lco_boundary || '--';
dbms_output.put_line('Request body>');
dbms_output.put_line(dbms_lob.substr(l_request_body, 4000, 1));
l_request_body_length := dbms_lob.getlength(l_request_body);
utl_http.set_wallet('file:/u02/oracle/upload/WALLET_TELEGRAM/', '******');
l_http_request := utl_http.begin_request(
url => 'https://api.telegram.org/bot<MY_KEY>/sendDocument',
method => 'POST',
http_version => 'HTTP/1.1'
);
postData := postData || 'chat_id=' || p_id || '&';
postData := postData || 'document=';
utl_http.set_header(l_http_request, 'Content-Type', 'multipart/form-data; boundary="' || lco_boundary || '"');
utl_http.set_header(l_http_request, 'Content-Length', l_request_body_length);
utl_http.write_text(l_http_request, postData);
while l_offset < l_request_body_length loop
dbms_lob.read(l_request_body, l_amount, l_offset, l_buffer);
utl_http.write_text(l_http_request, l_buffer);
l_offset := l_offset + l_amount;
end loop;
l_http_response := utl_http.get_response(l_http_request);
for i in 1 .. utl_http.get_header_count(l_http_response) loop
utl_http.get_header(l_http_response, i, l_response_header_name, l_response_header_value);
l_response_header_value);
end loop;
utl_http.read_text(l_http_response, l_response_body, 32767);
dbms_output.put_line(l_response_body);
if l_http_request.private_hndl is not null then
utl_http.end_request(l_http_request);
end if;
if l_http_response.private_hndl is not null then
utl_http.end_response(l_http_response);
end if;
exception
when others then
if l_http_request.private_hndl is not null then
utl_http.end_request(l_http_request);
end if;
if l_http_response.private_hndl is not null then
utl_http.end_response(l_http_response);
end if;
raise;
end;