Introduce a /version API (#667)

<!-- Provide a brief summary of your changes -->

## Motivation and Context
<!-- Why is this change needed? What problem does it solve? -->
The following PR introduces a `/version` API that serves the build
details along with the version of the API server being served. The
`/version` endpoint allows users to programmatically query which exact
version of the registry is running in production for debugging.
~~auditing, and compatibility checks~~.

## How Has This Been Tested?
<!-- Have you tested this in a real application? Which scenarios were
tested? -->

## Breaking Changes
<!-- Will users need to update their code or configurations? -->

## Types of changes
<!-- What types of changes does your code introduce? Put an `x` in all
the boxes that apply: -->
- [ ] Bug fix (non-breaking change which fixes an issue)
- [ ] New feature (non-breaking change which adds functionality)
- [ ] Breaking change (fix or feature that would cause existing
functionality to change)
- [ ] Documentation update

## Checklist
<!-- Go over all the following points, and put an `x` in all the boxes
that apply. -->
- [ ] I have read the [MCP
Documentation](https://modelcontextprotocol.io)
- [ ] My code follows the repository's style guidelines
- [ ] New and existing tests pass locally
- [ ] I have added appropriate error handling
- [ ] I have added or updated documentation as needed

## Additional context
<!-- Add any other context, implementation notes, or design decisions
-->

Signed-off-by: Radoslav Dimitrov <radoslav@stacklok.com>

internal/api/handlers/v0/version.go

@@ -0,0 +1,32 @@
+package v0
+
+import (
+	"context"
+	"net/http"
+	"strings"
+
+	"github.com/danielgtaylor/huma/v2"
+)
+
+// VersionBody represents the version information
+type VersionBody struct {
+	Version   string `json:"version" example:"v1.0.0" doc:"Application version"`
+	GitCommit string `json:"git_commit" example:"abc123d" doc:"Git commit SHA"`
+	BuildTime string `json:"build_time" example:"2025-10-14T12:00:00Z" doc:"Build timestamp"`
+}
+
+// RegisterVersionEndpoint registers the version endpoint with a custom path prefix
+func RegisterVersionEndpoint(api huma.API, pathPrefix string, versionInfo *VersionBody) {
+	huma.Register(api, huma.Operation{
+		OperationID: "get-version" + strings.ReplaceAll(pathPrefix, "/", "-"),
+		Method:      http.MethodGet,
+		Path:        pathPrefix + "/version",
+		Summary:     "Get version information",
+		Description: "Returns the version, git commit, and build time of the registry application",
+		Tags:        []string{"version"},
+	}, func(_ context.Context, _ *struct{}) (*Response[VersionBody], error) {
+		return &Response[VersionBody]{
+			Body: *versionInfo,
+		}, nil
+	})
+}

internal/api/handlers/v0/version_test.go

@@ -0,0 +1,76 @@
+package v0_test
+
+import (
+	"net/http"
+	"net/http/httptest"
+	"testing"
+
+	"github.com/danielgtaylor/huma/v2"
+	"github.com/danielgtaylor/huma/v2/adapters/humago"
+	"github.com/stretchr/testify/assert"
+
+	v0 "github.com/modelcontextprotocol/registry/internal/api/handlers/v0"
+)
+
+func TestVersionEndpoint(t *testing.T) {
+	// Test cases
+	testCases := []struct {
+		name         string
+		versionInfo  *v0.VersionBody
+		expectedBody map[string]string
+	}{
+		{
+			name: "returns version information",
+			versionInfo: &v0.VersionBody{
+				Version:   "v1.2.3",
+				GitCommit: "abc123def456",
+				BuildTime: "2025-10-14T12:00:00Z",
+			},
+			expectedBody: map[string]string{
+				"version":    "v1.2.3",
+				"git_commit": "abc123def456",
+				"build_time": "2025-10-14T12:00:00Z",
+			},
+		},
+		{
+			name: "returns dev version information",
+			versionInfo: &v0.VersionBody{
+				Version:   "dev",
+				GitCommit: "unknown",
+				BuildTime: "unknown",
+			},
+			expectedBody: map[string]string{
+				"version":    "dev",
+				"git_commit": "unknown",
+				"build_time": "unknown",
+			},
+		},
+	}
+
+	for _, tc := range testCases {
+		t.Run(tc.name, func(t *testing.T) {
+			// Create a new test API
+			mux := http.NewServeMux()
+			api := humago.New(mux, huma.DefaultConfig("Test API", "1.0.0"))
+
+			// Register the version endpoint
+			v0.RegisterVersionEndpoint(api, "/v0", tc.versionInfo)
+
+			// Create a test request
+			req := httptest.NewRequest(http.MethodGet, "/v0/version", nil)
+			w := httptest.NewRecorder()
+
+			// Serve the request
+			mux.ServeHTTP(w, req)
+
+			// Check the status code
+			assert.Equal(t, http.StatusOK, w.Code)
+
+			// Check the response body
+			body := w.Body.String()
+			assert.Contains(t, body, `"version":"`+tc.expectedBody["version"]+`"`)
+			assert.Contains(t, body, `"git_commit":"`+tc.expectedBody["git_commit"]+`"`)
+			assert.Contains(t, body, `"build_time":"`+tc.expectedBody["build_time"]+`"`)
+		})
+	}
+}