feat(tools/firestore-get-rules)!: Add databaseId to the firestore source and firestore-get-rules tool (#1505)

## Description

---
Added `DatabaseId` to the Firestore Source and Firestore-Get-Rules tool
for fetching the granular per-database rules instead of rules for the
default database.

## PR Checklist

---
> Thank you for opening a Pull Request! Before submitting your PR, there
are a
> few things you can do to make sure it goes smoothly:

- [x] Make sure you reviewed

[CONTRIBUTING.md](https://github.com/googleapis/genai-toolbox/blob/main/CONTRIBUTING.md)
- [x] Make sure to open an issue as a

[bug/issue](https://github.com/googleapis/genai-toolbox/issues/new/choose)
before writing your code! That way we can discuss the change, evaluate
  designs, and agree on the general idea
- [x] Ensure the tests and linter pass
- [x] Code coverage does not decrease (if any source code was changed)
- [x] Appropriate docs were updated (if necessary)
- [x] Make sure to add `!` if this involve a breaking change

---------

Co-authored-by: Averi Kitsch <akitsch@google.com>

internal/sources/firestore/firestore.go

@@ -78,6 +78,7 @@ func (r Config) Initialize(ctx context.Context, tracer trace.Tracer) (sources.So
 		Client:      client,
 		RulesClient: rulesClient,
 		ProjectId:   r.Project,
+		DatabaseId:  r.Database,
 	}
 	return s, nil
 }
@@ -91,6 +92,7 @@ type Source struct {
 	Client      *firestore.Client
 	RulesClient *firebaserules.Service
 	ProjectId   string `yaml:"projectId"`
+	DatabaseId  string `yaml:"databaseId"`
 }
 
 func (s *Source) SourceKind() string {
@@ -110,6 +112,10 @@ func (s *Source) GetProjectId() string {
 	return s.ProjectId
 }
 
+func (s *Source) GetDatabaseId() string {
+	return s.DatabaseId
+}
+
 func initFirestoreConnection(
 	ctx context.Context,
 	tracer trace.Tracer,

internal/tools/firestore/firestoregetrules/firestoregetrules.go

@@ -44,6 +44,7 @@ func newConfig(ctx context.Context, name string, decoder *yaml.Decoder) (tools.T
 type compatibleSource interface {
 	FirebaseRulesClient() *firebaserules.Service
 	GetProjectId() string
+	GetDatabaseId() string
 }
 
 // validate compatible sources are still compatible
@@ -96,6 +97,7 @@ func (cfg Config) Initialize(srcs map[string]sources.Source) (tools.Tool, error)
 		AuthRequired: cfg.AuthRequired,
 		RulesClient:  s.FirebaseRulesClient(),
 		ProjectId:    s.GetProjectId(),
+		DatabaseId:   s.GetDatabaseId(),
 		manifest:     tools.Manifest{Description: cfg.Description, Parameters: parameters.Manifest(), AuthRequired: cfg.AuthRequired},
 		mcpManifest:  mcpManifest,
 	}
@@ -113,20 +115,21 @@ type Tool struct {
 
 	RulesClient *firebaserules.Service
 	ProjectId   string
+	DatabaseId  string
 	manifest    tools.Manifest
 	mcpManifest tools.McpManifest
 }
 
 func (t Tool) Invoke(ctx context.Context, params tools.ParamValues, accessToken tools.AccessToken) (any, error) {
 	// Get the latest release for Firestore
-	releaseName := fmt.Sprintf("projects/%s/releases/cloud.firestore", t.ProjectId)
+	releaseName := fmt.Sprintf("projects/%s/releases/cloud.firestore/%s", t.ProjectId, t.DatabaseId)
 	release, err := t.RulesClient.Projects.Releases.Get(releaseName).Context(ctx).Do()
 	if err != nil {
 		return nil, fmt.Errorf("failed to get latest Firestore release: %w", err)
 	}
 
 	if release.RulesetName == "" {
-		return nil, fmt.Errorf("no active Firestore rules were found in project '%s'", t.ProjectId)
+		return nil, fmt.Errorf("no active Firestore rules were found in project '%s' and database '%s'", t.ProjectId, t.DatabaseId)
 	}
 
 	// Get the ruleset content