Refactor codebase, introduce relaymode package, update constants and improve consistency

- Refactor constant definitions and organization
- Clean up package level variables and functions
- Introduce new `relaymode` and `apitype` packages for constant definitions
- Refactor and simplify code in several packages including `openai`, `relay/channel/baidu`, `relay/util`, `relay/controller`, `relay/channeltype`
- Add helper functions in `relay/channeltype` package to convert channel type constants to corresponding API type constants
- Remove deprecated functions such as `ResponseText2Usage` from `relay/channel/openai/helper.go`
- Modify code in `relay/util/validation.go` and related files to use new `validator.ValidateTextRequest` function
- Rename `util` package to `relaymode` and update related imports in several packages

common/random/main.go

@@ -0,0 +1,62 @@
+package random
+
+import (
+	"math/rand"
+	"strings"
+	"time"
+
+	"github.com/google/uuid"
+)
+
+func GetUUID() string {
+	code := uuid.New().String()
+	code = strings.Replace(code, "-", "", -1)
+	return code
+}
+
+const keyChars = "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ"
+const keyNumbers = "0123456789"
+
+func init() {
+	rand.Seed(time.Now().UnixNano())
+}
+
+func GenerateKey() string {
+	rand.Seed(time.Now().UnixNano())
+	key := make([]byte, 48)
+	for i := 0; i < 16; i++ {
+		key[i] = keyChars[rand.Intn(len(keyChars))]
+	}
+	uuid_ := GetUUID()
+	for i := 0; i < 32; i++ {
+		c := uuid_[i]
+		if i%2 == 0 && c >= 'a' && c <= 'z' {
+			c = c - 'a' + 'A'
+		}
+		key[i+16] = c
+	}
+	return string(key)
+}
+
+func GetRandomString(length int) string {
+	rand.Seed(time.Now().UnixNano())
+	key := make([]byte, length)
+	for i := 0; i < length; i++ {
+		key[i] = keyChars[rand.Intn(len(keyChars))]
+	}
+	return string(key)
+}
+
+func GetRandomNumberString(length int) string {
+	rand.Seed(time.Now().UnixNano())
+	key := make([]byte, length)
+	for i := 0; i < length; i++ {
+		key[i] = keyNumbers[rand.Intn(len(keyNumbers))]
+	}
+	return string(key)
+}
+
+// RandRange returns a random number between min and max (max is not included)
+func RandRange(min, max int) int {
+	return min + rand.Intn(max-min)
+}