feat(api): Describe the API from the code and serve the description

.gitignore

@@ -41,3 +41,4 @@ config.yaml
 tmp/
 temp/
 .tmp/
+/genspec

go.mod

@@ -41,6 +41,7 @@ require (
 	go.opentelemetry.io/otel/sdk/metric v1.41.0
 	golang.org/x/crypto v0.51.0
 	golang.org/x/oauth2 v0.36.0
+	golang.org/x/tools v0.45.0
 	gopkg.in/yaml.v3 v3.0.1
 	modernc.org/sqlite v1.47.0
 )
@@ -201,6 +202,7 @@ require (
 	go.yaml.in/yaml/v3 v3.0.4 // indirect
 	go.yaml.in/yaml/v4 v4.0.0-rc.4 // indirect
 	golang.org/x/arch v0.18.0 // indirect
+	golang.org/x/mod v0.37.0 // indirect
 	golang.org/x/net v0.55.0 // indirect
 	golang.org/x/sync v0.21.0 // indirect
 	golang.org/x/sys v0.46.0 // indirect

internal/api/backup_handlers.go

@@ -48,7 +48,7 @@ func (s *Server) listBackups(c *gin.Context) {
 		backups = filtered
 	}
 
-	c.JSON(http.StatusOK, gin.H{"backups": backups})
+	c.JSON(http.StatusOK, NewList(backups, "backups"))
 }
 
 func (s *Server) getBackup(c *gin.Context) {
@@ -140,7 +140,7 @@ func (s *Server) listDeploymentBackups(c *gin.Context) {
 		return
 	}
 
-	c.JSON(http.StatusOK, gin.H{"backups": backups})
+	c.JSON(http.StatusOK, NewList(backups, "backups"))
 }
 
 func (s *Server) deleteBackup(c *gin.Context) {

internal/api/openapi.go

@@ -0,0 +1,18 @@
+package api
+
+import (
+	_ "embed"
+	"net/http"
+
+	"github.com/gin-gonic/gin"
+)
+
+// Generated by tools/genspec and checked against the routes in CI. Serving it lets a client ask
+// the instance it is talking to what that instance accepts.
+//
+//go:embed openapi.json
+var openAPISpec []byte
+
+func (s *Server) getOpenAPISpec(c *gin.Context) {
+	c.Data(http.StatusOK, "application/json; charset=utf-8", openAPISpec)
+}