feat(sources/mssql): add app name to MSSQL (#1620)

## Description

---
Add auditable application name to mssql sources. Query the db with:
```
SELECT session_id, program_name
FROM sys.dm_exec_sessions;
```

## 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:

- [ ] Make sure you reviewed

[CONTRIBUTING.md](https://github.com/googleapis/genai-toolbox/blob/main/CONTRIBUTING.md)
- [ ] 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
- [ ] Ensure the tests and linter pass
- [ ] Code coverage does not decrease (if any source code was changed)
- [ ] Appropriate docs were updated (if necessary)
- [ ] Make sure to add `!` if this involve a breaking change

🛠️ Fixes #<issue_number_goes_here>

internal/sources/cloudsqlmssql/cloud_sql_mssql.go

@@ -111,20 +111,25 @@ func initCloudSQLMssqlConnection(ctx context.Context, tracer trace.Tracer, name,
 	ctx, span := sources.InitConnectionSpan(ctx, tracer, SourceKind, name)
 	defer span.End()
 
-	// Create dsn
-	query := fmt.Sprintf("database=%s&cloudsql=%s:%s:%s", dbname, project, region, instance)
-	url := &url.URL{
-		Scheme:   "sqlserver",
-		User:     url.UserPassword(user, pass),
-		Host:     ipAddress,
-		RawQuery: query,
-	}
-
-	// Get dial options
 	userAgent, err := util.UserAgentFromContext(ctx)
 	if err != nil {
 		return nil, err
 	}
+
+	// Create dsn
+	query := url.Values{}
+	query.Add("app name", userAgent)
+	query.Add("database", dbname)
+	query.Add("cloudsql", fmt.Sprintf("%s:%s:%s", project, region, instance))
+
+	url := &url.URL{
+		Scheme:   "sqlserver",
+		User:     url.UserPassword(user, pass),
+		Host:     ipAddress,
+		RawQuery: query.Encode(),
+	}
+
+	// Get dial options
 	opts, err := sources.GetCloudSQLOpts(ipType, userAgent, false)
 	if err != nil {
 		return nil, err

internal/sources/mssql/mssql.go

@@ -22,6 +22,7 @@ import (
 
 	"github.com/goccy/go-yaml"
 	"github.com/googleapis/genai-toolbox/internal/sources"
+	"github.com/googleapis/genai-toolbox/internal/util"
 	_ "github.com/microsoft/go-mssqldb"
 	"go.opentelemetry.io/otel/trace"
 )
@@ -114,8 +115,13 @@ func initMssqlConnection(
 	ctx, span := sources.InitConnectionSpan(ctx, tracer, SourceKind, name)
 	defer span.End()
 
+	userAgent, err := util.UserAgentFromContext(ctx)
+	if err != nil {
+		userAgent = "genai-toolbox"
+	}
 	// Create dsn
 	query := url.Values{}
+	query.Add("app name", userAgent)
 	query.Add("database", dbname)
 	if encrypt != "" {
 		query.Add("encrypt", encrypt)