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/network/ip.go

@@ -0,0 +1,52 @@
+package network
+
+import (
+	"context"
+	"fmt"
+	"github.com/songquanpeng/one-api/common/logger"
+	"net"
+	"strings"
+)
+
+func splitSubnets(subnets string) []string {
+	res := strings.Split(subnets, ",")
+	for i := 0; i < len(res); i++ {
+		res[i] = strings.TrimSpace(res[i])
+	}
+	return res
+}
+
+func isValidSubnet(subnet string) error {
+	_, _, err := net.ParseCIDR(subnet)
+	if err != nil {
+		return fmt.Errorf("failed to parse subnet: %w", err)
+	}
+	return nil
+}
+
+func isIpInSubnet(ctx context.Context, ip string, subnet string) bool {
+	_, ipNet, err := net.ParseCIDR(subnet)
+	if err != nil {
+		logger.Errorf(ctx, "failed to parse subnet: %s", err.Error())
+		return false
+	}
+	return ipNet.Contains(net.ParseIP(ip))
+}
+
+func IsValidSubnets(subnets string) error {
+	for _, subnet := range splitSubnets(subnets) {
+		if err := isValidSubnet(subnet); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+func IsIpInSubnets(ctx context.Context, ip string, subnets string) bool {
+	for _, subnet := range splitSubnets(subnets) {
+		if isIpInSubnet(ctx, ip, subnet) {
+			return true
+		}
+	}
+	return false
+}