Serve OpenAPI 3.0 spec at /openapi.v1.json (#37038)

Add a build-time conversion step that transforms the existing Swagger
2.0 spec into an OpenAPI 3.0 spec. The OAS3 spec is served alongside the
existing Swagger 2.0 spec, enabling API clients that require OAS3 to
generate code directly from Gitea's API.

This is not to be an answer to how gitea handles OAS3 long term,
but a way to use what we have to move a step forward.

---------

Signed-off-by: wxiaoguang <wxiaoguang@gmail.com>
Co-authored-by: Claude (Opus 4.7) <noreply@anthropic.com>
Co-authored-by: silverwind <me@silverwind.io>
Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>

modules/structs/repo.go

@@ -8,6 +8,15 @@ import (
 	"time"
 )
 
+// ObjectFormatName is the git hash algorithm used by a repository.
+// swagger:enum ObjectFormatName
+type ObjectFormatName string
+
+const (
+	ObjectFormatSHA1   ObjectFormatName = "sha1"
+	ObjectFormatSHA256 ObjectFormatName = "sha256"
+)
+
 // Permission represents a set of permissions
 type Permission struct {
 	Admin bool `json:"admin"` // Admin indicates if the user is an administrator of the repository.
@@ -114,8 +123,7 @@ type Repository struct {
 	Internal                      bool             `json:"internal"`
 	MirrorInterval                string           `json:"mirror_interval"`
 	// ObjectFormatName of the underlying git repository
-	// enum: ["sha1","sha256"]
-	ObjectFormatName string `json:"object_format_name"`
+	ObjectFormatName ObjectFormatName `json:"object_format_name"`
 	// swagger:strfmt date-time
 	MirrorUpdated time.Time     `json:"mirror_updated"`
 	RepoTransfer  *RepoTransfer `json:"repo_transfer,omitempty"`
@@ -153,8 +161,7 @@ type CreateRepoOption struct {
 	// enum: ["default","collaborator","committer","collaboratorcommitter"]
 	TrustModel string `json:"trust_model"`
 	// ObjectFormatName of the underlying git repository, empty string for default (sha1)
-	// enum: ["sha1","sha256"]
-	ObjectFormatName string `json:"object_format_name" binding:"MaxSize(6)"`
+	ObjectFormatName ObjectFormatName `json:"object_format_name" binding:"MaxSize(6)"`
 }
 
 // EditRepoOption options when editing a repository's properties