Implement send-email Container

[vahid-dan]

We are in need of a container to send daily emails to a list of recipients including a message and a few file attachments. We should be able to run this container once a day at a specific time on the IBM Cloud.

• The container should have a similar structure as FLARE containers (naming convention, usage of Bash3 BoilerPlate, usage of config file, etc.).
• Use "S-nail" as the mail processing system.
• Set up a Gmail account on the S-nail authenticate on Gmail and send the email via Gmail.
• Encode the password for the Gmail account in the s-nail config file so that it would be secure to publish the image to the public.
• The attachments should be downloaded from S3 storage based on a filename prefix and the current date.
• The list of recipients, the filename prefix for the attachments, and the message body should be read from a config file.

[vahid-dan]

The YAML file should include the body message, the list of attachments, and the list of recipients. The lists can be of any length. For instance, we may have just one recipient or multiple recipients and we should be able to add or remove to the lists at any time.

The attachments should have a direct URL for the file (such as a URL to a raw GitHub file) or a link to an S3 object.

Sample YAML File:

gmail:
    username: "someone@gmail.com"
    password-hash: "password in plain text here"
    from: "friendly name"
email:
    subject: "email subject here"
    body: "body message here"
    attachments:
      - "https://github.com/FLARE-forecast/SUNP-data/raw/sunp-graphs/sunpMetDataFigures_<date>.pdf
      - "https://github.com/FLARE-forecast/SUNP-data/raw/sunp-graphs/sunpWaterQualityDataFigures_<date>.pdf"
      - s3-object1
      - s3-object2
      - s3-object3
      - github-url3
    recepients:
      - recepient1
      - recepient2
      - recepient3

[vahid-dan]

@Yun-Jung, Now that the basic implementation is in place, we need to enhance it:

• The code should be able to automatically skip the local attachments and GitHub attachments if they don't exist.
• The structure of the container (code, config, Bash3BoilerPlate) and the file naming should be similar to other FLARE containers. We should be able to do the initial setup by running flare-install.sh script directly from the web and then running the container by running flare-host.sh script from the host.

[vahid-dan]

@Yun-Jung, If the attachments are not available due to an error, we should add a notification message to the email. It's confusing if the email says the graphs are attached, but there is no attachment.