Support case-insensitive base64 encode variant argument

Author: alexcams

pkg/ottl/ottlfuncs/README.md

@@ -587,7 +587,7 @@ Examples:
 The `Base64Encode` Converter takes a string and returns a base64 encoded string.
 
 `value` is a string to encode.
-`variant` (optional) is the base64 encoding variant to use. Valid values are `base64` (standard, with padding), `base64-raw` (standard, no padding), `base64-url` (URL-safe, with padding), or `base64-raw-url` (URL-safe, no padding). Defaults to `base64` if not specified.
+`variant` (optional) is the base64 encoding variant to use. Valid values are `base64` (standard, with padding), `base64-raw` (standard, no padding), `base64-url` (URL-safe, with padding), or `base64-raw-url` (URL-safe, no padding). The variant name is case-insensitive. Defaults to `base64` if not specified.
 
 Examples:
 
@@ -602,6 +602,9 @@ Examples:
 
 - `Base64Encode(attributes["data"], "base64-raw")`
 
+
+- `Base64Encode(attributes["data"], "BASE64-URL")` # Variant names are case-insensitive
+
 ### Bool
 
 `Bool(value)`

pkg/ottl/ottlfuncs/func_base64encode.go

@@ -8,6 +8,7 @@ import (
 	"encoding/base64"
 	"errors"
 	"fmt"
+	"strings"
 
 	"github.com/open-telemetry/opentelemetry-collector-contrib/pkg/ottl"
 )
@@ -47,7 +48,7 @@ func Base64Encode[K any](target ottl.StringGetter[K], variant ottl.Optional[ottl
 			}
 		}
 
-		switch variantVal {
+		switch strings.ToLower(variantVal) {
 		case "base64":
 			return base64.StdEncoding.EncodeToString(data), nil
 		case "base64-raw":

pkg/ottl/ottlfuncs/func_base64encode_test.go

@@ -69,6 +69,24 @@ func TestBase64Encode(t *testing.T) {
 			variant: "base64-raw-url",
 			want:    "ZGF0YSt2YWx1ZXMvaXRlbXM",
 		},
+		{
+			name:    "case insensitive variant - BASE64",
+			value:   "test string",
+			variant: "BASE64",
+			want:    "dGVzdCBzdHJpbmc=",
+		},
+		{
+			name:    "case insensitive variant - Base64-Raw",
+			value:   "test string",
+			variant: "Base64-Raw",
+			want:    "dGVzdCBzdHJpbmc",
+		},
+		{
+			name:    "case insensitive variant - BASE64-URL",
+			value:   "data+values/items",
+			variant: "BASE64-URL",
+			want:    "ZGF0YSt2YWx1ZXMvaXRlbXM=",
+		},
 		{
 			name:          "unsupported type int",
 			value:         10,