refactor: streamline input handling in MetadataLookup method

- Updated the MetadataLookup method to utilize a switch statement for improved clarity in determining the lookup strategy based on input format.
- Simplified the logic for handling canonical, email, and username lookups, enhancing code readability and maintainability.

Jira Ticket: https://linuxfoundation.atlassian.net/browse/LFXV2-499

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Signed-off-by: Mauricio Zanetti Salomao <mauriciozanetti86@gmail.com>

Author: mauriciozanettisalomao

internal/infrastructure/mock/user.go

@@ -229,21 +229,22 @@ func (u *userWriter) MetadataLookup(ctx context.Context, input string) (*model.U
 	}
 
 	// Determine lookup strategy based on input format
-	if strings.Contains(input, "|") {
+	switch {
+	case strings.Contains(input, "|"):
 		// Input contains "|", use as sub for canonical lookup
 		user.Sub = input
 		user.UserID = input
 		user.Username = ""
 		user.PrimaryEmail = ""
 		slog.InfoContext(ctx, "mock: canonical lookup strategy", "sub", input)
-	} else if strings.Contains(input, "@") {
+	case strings.Contains(input, "@"):
 		// Input looks like an email, use for email search
 		user.PrimaryEmail = strings.ToLower(input) // Normalize email to lowercase
 		user.Sub = ""
 		user.UserID = ""
 		user.Username = ""
 		slog.InfoContext(ctx, "mock: email search strategy", "email", user.PrimaryEmail)
-	} else {
+	default:
 		// Input doesn't contain "|" or "@", use for username search
 		user.Username = input
 		user.Sub = ""