Support configuration variables on Gitea Actions (#24724)

Co-Author: @silverwind @wxiaoguang 
Replace: #24404

See:
- [defining configuration variables for multiple
workflows](https://docs.github.com/en/actions/learn-github-actions/variables#defining-configuration-variables-for-multiple-workflows)
- [vars
context](https://docs.github.com/en/actions/learn-github-actions/contexts#vars-context)

Related to:
- [x] protocol: https://gitea.com/gitea/actions-proto-def/pulls/7
- [x] act_runner: https://gitea.com/gitea/act_runner/pulls/157
- [x] act: https://gitea.com/gitea/act/pulls/43

#### Screenshoot
Create Variable:

![image](https://user-images.githubusercontent.com/33891828/236758288-032b7f64-44e7-48ea-b07d-de8b8b0e3729.png)


![image](https://user-images.githubusercontent.com/33891828/236758174-5203f64c-1d0e-4737-a5b0-62061dee86f8.png)

Workflow:
```yaml
  test_vars:
    runs-on: ubuntu-latest
    steps:
      - name: Print Custom Variables
        run: echo "${{ vars.test_key }}"
      - name: Try to print a non-exist var
        run: echo "${{ vars.NON_EXIST_VAR }}"
```

Actions Log:

![image](https://user-images.githubusercontent.com/33891828/236759075-af0c5950-368d-4758-a8ac-47a96e43b6e2.png)

---
This PR just implement the org / user (depends on the owner of the
current repository) and repo level variables, The Environment level
variables have not been implemented.
Because
[Environment](https://docs.github.com/en/actions/deployment/targeting-different-environments/using-environments-for-deployment#about-environments)
is a module separate from `Actions`. Maybe it would be better to create
a new PR to do it.

---------

Co-authored-by: silverwind <me@silverwind.io>
Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>
Co-authored-by: Giteabot <teabot@gitea.io>

models/secret/secret.go

@@ -5,38 +5,17 @@ package secret
 
 import (
 	"context"
-	"fmt"
-	"regexp"
+	"errors"
 	"strings"
 
 	"code.gitea.io/gitea/models/db"
 	secret_module "code.gitea.io/gitea/modules/secret"
 	"code.gitea.io/gitea/modules/setting"
 	"code.gitea.io/gitea/modules/timeutil"
-	"code.gitea.io/gitea/modules/util"
 
 	"xorm.io/builder"
 )
 
-type ErrSecretInvalidValue struct {
-	Name *string
-	Data *string
-}
-
-func (err ErrSecretInvalidValue) Error() string {
-	if err.Name != nil {
-		return fmt.Sprintf("secret name %q is invalid", *err.Name)
-	}
-	if err.Data != nil {
-		return fmt.Sprintf("secret data %q is invalid", *err.Data)
-	}
-	return util.ErrInvalidArgument.Error()
-}
-
-func (err ErrSecretInvalidValue) Unwrap() error {
-	return util.ErrInvalidArgument
-}
-
 // Secret represents a secret
 type Secret struct {
 	ID          int64
@@ -74,24 +53,11 @@ func init() {
 	db.RegisterModel(new(Secret))
 }
 
-var (
-	secretNameReg            = regexp.MustCompile("^[A-Z_][A-Z0-9_]*$")
-	forbiddenSecretPrefixReg = regexp.MustCompile("^GIT(EA|HUB)_")
-)
-
-// Validate validates the required fields and formats.
 func (s *Secret) Validate() error {
-	switch {
-	case len(s.Name) == 0 || len(s.Name) > 50:
-		return ErrSecretInvalidValue{Name: &s.Name}
-	case len(s.Data) == 0:
-		return ErrSecretInvalidValue{Data: &s.Data}
-	case !secretNameReg.MatchString(s.Name) ||
-		forbiddenSecretPrefixReg.MatchString(s.Name):
-		return ErrSecretInvalidValue{Name: &s.Name}
-	default:
-		return nil
+	if s.OwnerID == 0 && s.RepoID == 0 {
+		return errors.New("the secret is not bound to any scope")
 	}
+	return nil
 }
 
 type FindSecretsOptions struct {