Add API for License templates (#23009)

This adds a API for getting License templates. This tries to be as close
to the [GitHub
API](https://docs.github.com/en/rest/licenses?apiVersion=2022-11-28) as
possible, but Gitea does not support all features that GitHub has. I
think they should been added, but this out f the scope of this PR. You
should merge #23006 before this PR for security reasons.

routers/api/v1/api.go

@@ -719,6 +719,8 @@ func Routes(ctx gocontext.Context) *web.Route {
 		m.Post("/markup", bind(api.MarkupOption{}), misc.Markup)
 		m.Post("/markdown", bind(api.MarkdownOption{}), misc.Markdown)
 		m.Post("/markdown/raw", misc.MarkdownRaw)
+		m.Get("/licenses", misc.ListLicenseTemplates)
+		m.Get("/licenses/{name}", misc.GetLicenseTemplateInfo)
 		m.Group("/settings", func() {
 			m.Get("/ui", settings.GetGeneralUISettings)
 			m.Get("/api", settings.GetGeneralAPISettings)

routers/api/v1/misc/licenses.go

@@ -0,0 +1,76 @@
+// Copyright 2023 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package misc
+
+import (
+	"fmt"
+	"net/http"
+	"net/url"
+
+	"code.gitea.io/gitea/modules/context"
+	"code.gitea.io/gitea/modules/options"
+	repo_module "code.gitea.io/gitea/modules/repository"
+	"code.gitea.io/gitea/modules/setting"
+	api "code.gitea.io/gitea/modules/structs"
+	"code.gitea.io/gitea/modules/util"
+)
+
+// Returns a list of all License templates
+func ListLicenseTemplates(ctx *context.APIContext) {
+	// swagger:operation GET /licenses miscellaneous listLicenseTemplates
+	// ---
+	// summary: Returns a list of all license templates
+	// produces:
+	// - application/json
+	// responses:
+	//   "200":
+	//     "$ref": "#/responses/LicenseTemplateList"
+	response := make([]api.LicensesTemplateListEntry, len(repo_module.Licenses))
+	for i, license := range repo_module.Licenses {
+		response[i] = api.LicensesTemplateListEntry{
+			Key:  license,
+			Name: license,
+			URL:  fmt.Sprintf("%sapi/v1/licenses/%s", setting.AppURL, url.PathEscape(license)),
+		}
+	}
+	ctx.JSON(http.StatusOK, response)
+}
+
+// Returns information about a gitignore template
+func GetLicenseTemplateInfo(ctx *context.APIContext) {
+	// swagger:operation GET /licenses/{name} miscellaneous getLicenseTemplateInfo
+	// ---
+	// summary: Returns information about a license template
+	// produces:
+	// - application/json
+	// parameters:
+	// - name: name
+	//   in: path
+	//   description: name of the license
+	//   type: string
+	//   required: true
+	// responses:
+	//   "200":
+	//     "$ref": "#/responses/LicenseTemplateInfo"
+	//   "404":
+	//     "$ref": "#/responses/notFound"
+	name := util.PathJoinRelX(ctx.Params("name"))
+
+	text, err := options.License(name)
+	if err != nil {
+		ctx.NotFound()
+		return
+	}
+
+	response := api.LicenseTemplateInfo{
+		Key:  name,
+		Name: name,
+		URL:  fmt.Sprintf("%sapi/v1/licenses/%s", setting.AppURL, url.PathEscape(name)),
+		Body: string(text),
+		// This is for combatibilty with the GitHub API. This Text is for some reason added to each License response.
+		Implementation: "Create a text file (typically named LICENSE or LICENSE.txt) in the root of your source code and copy the text of the license into the file",
+	}
+
+	ctx.JSON(http.StatusOK, response)
+}

routers/api/v1/swagger/misc.go

@@ -14,6 +14,20 @@ type swaggerResponseServerVersion struct {
 	Body api.ServerVersion `json:"body"`
 }
 
+// LicenseTemplateList
+// swagger:response LicenseTemplateList
+type swaggerResponseLicensesTemplateList struct {
+	// in:body
+	Body []api.LicensesTemplateListEntry `json:"body"`
+}
+
+// LicenseTemplateInfo
+// swagger:response LicenseTemplateInfo
+type swaggerResponseLicenseTemplateInfo struct {
+	// in:body
+	Body api.LicenseTemplateInfo `json:"body"`
+}
+
 // StringSlice
 // swagger:response StringSlice
 type swaggerResponseStringSlice struct {