Add customisable server email capabilities

[drussell-x]

In order to facilitate sending announcement (and potentially other) emails from the OMERO server instance the sendEmail method or whatever the new method is called will need to accept several parameters:

This would send a message with the defined subject and message. I currently have no need to send email with CCs or recipients, but I think it would make sense to add support for this initially in case someone wishes to use it. Thus it is possible to specify a list of experimenters and groups. It also accepts a list of strings of arbitrary email addresses. This is useful for CCing a departmental mailing list or similar. This is especially important in an LDAP environment as the server is accessible to new users at any time so they'd need to know about a service disruption up-front etc.

// Sends a single message to a collection of experimenters resolved from the Experimenter
// and ExperimenterGroup lists.
boolean sendEmail(
    boolean all,
    List<Experimenter> experimentersTo,
    List<ExperimenterGroup> groupsTo,
    List<String> cc,
    String subject,
    String message
)

// Sends a message many times, individually (standard automated email procedure)
boolean sendMassEmail(
    boolean all,
    List<Experimenter> experimentersTo,
    List<ExperimenterGroup> groupsTo,
    List<String> additionalRecipients,
    String subject,
    String message
)

I'm undecided what the return types should be. All success/fail is one option. What about a partial failure? What about a failure to resolve a specified user as they don't have an email address, should that fail silently?

It might also be nice to have the capability for an admin to check if the server
has the capability to send emails. Obviously it can't really check if the emails
are correctly being sent, but just that the settings are present in the server
to enable it to send email.

boolean isEmailEnabled()

Some of the required functionality can be recoded in Java from ​here. I think group resolution to email lists is probably the missing piece there.

Cheers,

Douglas

[drussell-x]

Accidental duplicate of ​http://trac.openmicroscopy.org.uk/ome/ticket/11768