lib/http: refactoring "multipart/form-data" parameters in ClientRequest

Previously, ClientRequest with type RequestTypeMultipartForm pass the
type "map[string][]byte" in Params.
This type hold the file upload, where key is the file name and []byte is
content of file.
Unfortunately, this model does not correct because a
"multipart/form-data" can contains different field name and file name,
for example

  --boundary
  Content-Disposition: form-data; name="field0"; filename="file0"
  Content-Type: application/octet-stream

  <Content of file0>

This changes fix this by changing the parameter type for
RequestTypeMultipartForm to [*multipart.Form], which affect several
functions including [Client.PutFormData] and [GenerateFormData].

We also add new function [CreateMultipartFileHeader] to help creating
[multipart.FileHeader] from raw bytes, that can be assigned to
[*multipart.Form].

1 files changed, 6 insertions, 3 deletions

diff --git a/lib/http/client_example_test.go b/lib/http/client_example_test.go
index 7b72cba1..22b24285 100644
--- a/lib/http/client_example_test.go
+++ b/lib/http/client_example_test.go
@@ -4,6 +4,7 @@ import (
 	"crypto/rand"
 	"fmt"
 	"log"
+	"mime/multipart"
 	"strings"
 
 	libhttp "git.sr.ht/~shulhan/pakakeh.go/lib/http"
@@ -15,9 +16,11 @@ func ExampleGenerateFormData() {
 	// NOTE: do not do this on real code.
 	rand.Reader = mock.NewRandReader([]byte(`randomseed`))
 
-	var data = map[string][]byte{
-		`name`: []byte(`test.txt`),
-		`size`: []byte(`42`),
+	var data = &multipart.Form{
+		Value: map[string][]string{
+			`name`: []string{`test.txt`},
+			`size`: []string{`42`},
+		},
 	}
 
 	var (