Remove leftover bson tags from the Go structs (#327)

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

## Motivation and Context
<!-- Why is this change needed? What problem does it solve? -->
The following PR removes the now obsolete bson tags (we moved away from
MongoDB).

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

## Breaking Changes
<!-- Will users need to update their code or configurations? -->
No

## 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
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-->

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

pkg/api/v0/types.go

@@ -8,18 +8,18 @@ import (
 
 // RegistryExtensions represents registry-generated metadata
 type RegistryExtensions struct {
-	ID          string    `json:"id" bson:"_id"`
-	PublishedAt time.Time `json:"published_at" bson:"published_at"`
-	UpdatedAt   time.Time `json:"updated_at,omitempty" bson:"updated_at,omitempty"`
-	IsLatest    bool      `json:"is_latest" bson:"is_latest"`
-	ReleaseDate string    `json:"release_date" bson:"release_date"`
+	ID          string    `json:"id"`
+	PublishedAt time.Time `json:"published_at"`
+	UpdatedAt   time.Time `json:"updated_at,omitempty"`
+	IsLatest    bool      `json:"is_latest"`
+	ReleaseDate string    `json:"release_date"`
 }
 
 // ServerRecord represents the unified storage and API response model
 type ServerRecord struct {
-	Server                          model.ServerJSON       `json:"server" bson:"server"`                                                    // Pure MCP server.json
-	XIOModelContextProtocolRegistry RegistryExtensions     `json:"x-io.modelcontextprotocol.registry,omitempty" bson:"registry_extensions"` // Registry-generated data
-	XPublisher                      map[string]interface{} `json:"x-publisher,omitempty" bson:"publisher_extensions"`                       // x-publisher extensions
+	Server                          model.ServerJSON       `json:"server"`                                                    // Pure MCP server.json
+	XIOModelContextProtocolRegistry RegistryExtensions     `json:"x-io.modelcontextprotocol.registry,omitempty"` // Registry-generated data
+	XPublisher                      map[string]interface{} `json:"x-publisher,omitempty"`                       // x-publisher extensions
 }
 
 // ServerListResponse represents the paginated server list response