addContactToGroup

Adds a contact to a specific group.

This method adds a contact, identified by contactId, to a group specified by groupId. The result is returned as a RainbowResult, indicating success or failure. Upon success, the group's details are updated in the groups property.

Validation Rules:

• groupId must not be null or empty.

• contactId must not be null or empty.

Behavior:

• If groupId or contactId is null or empty, the function returns a Failure with an appropriate error message.

• If the contact is successfully added, a Success is returned.

• If the operation fails, a Failure containing an error is returned.

Parameters