Improve domain name validation

[Genne23v]

Resolve #185

Adding domain name validation as following rules

• Domain name pattern should be [name].[studentId].rootDomain.com(.)
• Domain name can contain only alphanumerical characters, -, and _
• Domain name should not start or end with -
• Domain name cannot contain multiple consecutive - or _
• Domain name can contain uppercase in UI but it is converted to lowercase before validation
• studentId only contains alphanumerical characters

Also domain name is lowercased before adding it to Route 53, but original name is stored in DB