Adds Goslmailer install to allow for SLURM notifications

[rumiah-safe]

Adds Goslmailer ansible playbook. This installs Mutt and all requisite config files and directories from our fork of goslmailer. README contains instructions on how to run the script and where to find the secrets. They are entered into the prompts that ansible makes.

Issue: #47

This does overwrite the mutt local config to ensure it functions correctly and by default it is blank. However, if, in the future other systems, want to use mutt we should look into integrating them properly.

Testing:

Installed multiple times to test idempotency.
Uninstalled multiple times to test idempotency.

Used this script to test the functionality of the service using my email as the sending email during installation:

#SBATCH --nodes=1
#SBATCH --time=10:00
#SBATCH --partition=compute  # OPTIONAL can be removed to run on big/normal partition
#SBATCH --job-name=Example
#SBATCH --mail-user=mailto:[email protected],slack:U059RL6PSKC
#SBATCH --mail-type=ALL

gcc --version # if you print it out here it'll be 4.8.5
sleep 5

# Recommended way if you want to enable gcc version 10 for the "sbatch" session
source /opt/rh/devtoolset-10/enable

gcc --version # if you print it out again here it'll be version 10

sleep 5

Then used this script to test failing notifications:

#SBATCH --nodes=1
#SBATCH --time=10:00
#SBATCH --partition=compute  # OPTIONAL can be removed to run on big/normal partition
#SBATCH --job-name=Example
#SBATCH --mail-user=mailto:[email protected],slack:U059RL6PSKC
#SBATCH --mail-type=ALL

gcc --version # if you print it out here it'll be 4.8.5
sleep 5

exit 1
# Recommended way if you want to enable gcc version 10 for the "sbatch" session
source /opt/rh/devtoolset-10/enable

gcc --version # if you print it out again here it'll be version 10

sleep 5

All of this handling is done by slurm and without any edit from my config so the rest of the notifications are expected to work and appear to, but I am unaware of how to create some of the situations that they notify for.

[steven-safeai]

Some comments.

Additionally where and how is the token set.
Update the README docs are important.

[steven-safeai]

Please reference the git issue somewhere in the pr so I can go back to look at it as well.

[rumiah-safe]

Sorry I shouldn't have pinged you yet I was still writing the request

[steven-safeai]

One last thing before I forget. Squash or fixup your commits before merging.

[andriy-safe-ai]

LGTM

[steven-safeai]

Squish them merge :)