Add a status field indicating if a server is deprecated or active (#210)

The following PR adds a new server `status` field to support the status
of servers, like deprecated or active

Details:
* Add status field to server.json schema with 'active' and 'deprecated'
values
* Update OpenAPI spec to include status field in Server responses
* Add ServerStatus enum and field to Go model structs
* Update examples to demonstrate status field usage (`active` and
`deprecated`)

Since this is my first PR there's a good chance I might have missed
something so I'll appreciate any feedback to make this and any PRs in
the future easier for you to review 😃

Fixes: #181

## Motivation and Context
<!-- Why is this change needed? What problem does it solve? -->
The main goal is to have a way for server authors to notify registry
consumers that a server may no longer be maintained and shouldn't be
considered for using.

## 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)
- [x] 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. -->
- [x] 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>
Co-authored-by: Tadas Antanavicius <tadas@tadasant.com>

internal/model/model.go

@@ -10,6 +10,16 @@ const (
 	AuthMethodNone AuthMethod = "none"
 )
 
+// ServerStatus represents the lifecycle status of a server
+type ServerStatus string
+
+const (
+	// ServerStatusActive represents an actively maintained server (as asserted by the publisher)
+	ServerStatusActive ServerStatus = "active"
+	// ServerStatusDeprecated represents a server that is no longer actively maintained
+	ServerStatusDeprecated ServerStatus = "deprecated"
+)
+
 // Authentication holds information about the authentication method and credentials
 type Authentication struct {
 	Method  AuthMethod `json:"method,omitempty"`
@@ -114,6 +124,7 @@ type Server struct {
 	ID            string        `json:"id" bson:"id"`
 	Name          string        `json:"name" bson:"name"`
 	Description   string        `json:"description" bson:"description"`
+	Status        ServerStatus  `json:"status,omitempty" bson:"status,omitempty"`
 	Repository    Repository    `json:"repository" bson:"repository"`
 	VersionDetail VersionDetail `json:"version_detail" bson:"version_detail"`
 }