Email notifications should have default sender and subject

[e-pettersson-ericsson]

Description

Since we do not validate the values set for properties email.sender and email.subject in application.properties we should have default values for these properties in the EmailSender class. Otherwise we might run into problems sending email notifications with empty subjects/no sender.

Motivation

We shouldn't risk any failures when sending email notifications.

Exemplification

We can add default values when retrieving the properties in EmailSender to avoid null values.

Benefits

We will always have email sender and subject defined, even if users do not defined them in their application.properties.

Possible Drawbacks

None.

[e-pettersson-ericsson]

Since the code changes have been merged I'm closing this issue.