Testing workflow in admin_site.yaml

[arh4uwe]

The main purpose of this PR is to test the GitHub Actions workflow that I've defined in the new .github/workflows/admin_site.yaml, which is supposed to run whenever there is a push to the main branch. As a side effect of this PR, the following things will also be changed:

• The file api/README.md has been created. This file shows users how to use OpenAPI Generator to update the files in api/dart and api/java.
• The file infrastructure/sam/README.md has been updated. This file now accurately shows users how to use SAM to perform various tasks with our project.
• The file infrastructure/config/github/oidc-provider-arh4uwe.yaml has been created. This is a CloudFormation template for the AWS IAM role github-oidc-provider-arh4uwe-moralpain_dev, which is necessary for the admin_site workflow.
• The file infrastructure/events/event.json has been updated so that it works when used to run one of our lambda functions locally using SAM.
• The file infrastructure/events/submit_survey_event.json has been created specifically to be used to run the submitSurvey lambda function locally using SAM.

[arh4uwe]

Oops, wrong repo. Should have done a PR with my main branch.