Use another IMAP docker image that allows more connections

Since CI builds of #326 failed and I could reproduce this locally,
it turned out that running single tests or tests of a single directory
was no problem. However, executing all tests at once led to failing
IMAP connections. Apparently an increased number of allowed IMAP
connections fixes the problem (locally).

Signed-off-by: Christoph Wurst <christoph@winzerhof-wurst.at>

Remove wrong abstraction in IAccount and use impl instead

Signed-off-by: Christoph Wurst <christoph@winzerhof-wurst.at>

Add keyboard shortcut to compose a new message

Use a common base class for all tests

Add integration tests for outgoing messages with attachments

Signed-off-by: Christoph Wurst <christoph@winzerhof-wurst.at>

Signed-off-by: Christoph Wurst <christoph@winzerhof-wurst.at>

Signed-off-by: Christoph Wurst <christoph@winzerhof-wurst.at>

Signed-off-by: Christoph Wurst <christoph@winzerhof-wurst.at>

Fix IMAP tests

Signed-off-by: Christoph Wurst <christoph@winzerhof-wurst.at>

IMAP integration tests failed because the 'Drafts' mailbox
is not part of the automatically created ones, hence it was
removed now.

Signed-off-by: Christoph Wurst <christoph@winzerhof-wurst.at>

Fix test base class and namespace

Signed-off-by: Christoph Wurst <christoph@winzerhof-wurst.at>

Ignore template coverage as we don't test them

Signed-off-by: Christoph Wurst <christoph@winzerhof-wurst.at>

Add more unit tests for the autoconfig logic

Signed-off-by: Christoph Wurst <christoph@winzerhof-wurst.at>

Signed-off-by: Christoph Wurst <christoph@winzerhof-wurst.at>

Signed-off-by: Christoph Wurst <christoph@winzerhof-wurst.at>

Signed-off-by: Christoph Wurst <christoph@winzerhof-wurst.at>

Signed-off-by: Christoph Wurst <christoph@winzerhof-wurst.at>

Refactor and test connectivity test classes

* Use composition instead of inheritance
* Unit test classes
* Mock connections to external servers

Signed-off-by: Christoph Wurst <christoph@winzerhof-wurst.at>

Add IMAP integration test framework

Signed-off-by: Christoph Wurst <christoph@winzerhof-wurst.at>

Add a trait-based testing framework that automatically resets
the IMAP testing account before a test case is run to prevent
side effects and dependencies across different tests.
A simple self test was added to ensure the functionality works
as expected.
A new super class for integration tests was added which should
be used now instead of phpunit's class. This will allow to write
tests with less boilerplate code, as we can for example check
the usage of the IMAP test trait and reset accounts automatically.
This was inspired by the Laravel testing capabilities.

Signed-off-by: Christoph Wurst <christoph@winzerhof-wurst.at>

Add SMTP integration tests