[Bug]: Inconsistent naming convention in metadata folder: MailServerConnection uses PascalCase instead of kebab-case

### Apache Hop version?

2.14

### Java version?

17

### Operating system

Windows

### What happened?

While reviewing the metadata folders in the HOP project, I noticed that most metadata folder names follow the kebab-case naming convention (e.g., data-connection, pipeline, workflow). However, the Mail service metadata uses MailServerConnection, which is in PascalCase, breaking consistency.

### Issue Priority

Priority: 3

### Issue Component

Component: Metadata

Inspect the metadata folders named in the issue, especially MailServerConnection and the kebab-case examples data-connection, pipeline, and workflow. Identify the repository path and any references to the Mail service metadata, rename the folder consistently, and verify that the project still builds and the metadata remains discoverable.

Written by the indexing model from the issue text.