Add confirmation email lambda function and invoke it in post application endpoint

[nourshoreibah]

ℹ️ Issue
Closes https://www.notion.so/mahekagg/GI-72-Lambda-function-to-send-emails-using-SES-for-when-an-application-has-been-received-18a8b3e6836e80738281ca9f6e457d72?pvs=4

📝 Description

• Created a lambda function called giSendApplicationConfirmation
• Installed the lambda sdk
• Created a lambda nest.js service similar to the dynamoDB one and registered it
• Invoked the lambda function from the post applications endpoint

Notes:

• The current DTO for posting an application does not contain the site name, user first name, or user email. This means we need to query the user and sites table when posting a new application so we can send the email. We could fix this by adding more fields for the DTO and save some compute. For now, I just used the get user and get site endpoint to pull this information before sending the email.
• I hard coded the placeholder "30 days" (in the API not the lambda function) for application time frame

Verification
Added mock user to users table and posted a new application with swagger, confirmed that I got an email.

[nourshoreibah]

Also sorry there are random commits from my last ticket, i accidentally branched off from it. I merged main in though i think they'll go away once my last PR merges

[hams7504]

Tested it and it looks good to me!
Should be good to merge once you remove the SignUpPage.tsx file additions! (might have to merge with main)