Convert 2018 Housing Affordability API service to Fargate

[MikeTheCanuck]

Addresses #244 for the 2018 Housing Affordability API. Mirrors the work in #259 and #260, and implements similar changes as hackoregon/hackoregon-aws-infrastructure#84. Uses the migration procedure documented here.

Acceptance Criteria

Tests that will confirm the container has successfully migrated:

1. CloudFormation will report UPDATE_COMPLETE for the enhanced stack
2. ECS will report (a) "Launch Type FARGATE" for the service, (b) 1 Task Running at the Task level, and (c) at the Task detail level a "Started at" timestamp that is at least 5 minutes into the past (which indicates that the container stayed RUNNING long enough to pass the ALB health check cycle)
3. latest log in CloudWatch group for the associated service will show similar entries as current log output 10.180.9.210 [09/Aug/2019:20:52:04 +0000] GET /housing-affordability/ HTTP/1.1 200 23929 - ELB-HealthChecker/2.0 0.103165
4. browser requests to https://service.civicpdx.org/housing-affordability/api/permits/ will display a Swagger-schema-prettified response with count: 27794 and detailed JSON objects in the results section
5. latest CloudWatch logs will display a recent web request to /housing-affordability/api/permits/ with a 200 response code

[MikeTheCanuck]

Cloudwatch logs for the newly-deployed, active HA service report

10.180.18.40 [29/Sep/2019:01:29:55 +0000] GET /housing-affordability/ HTTP/1.1 200 19859 - ELB-HealthChecker/2.0 0.011672
10.180.18.40 [29/Sep/2019:01:29:58 +0000] GET /housing-affordability/api/permits/ HTTP/1.1 200 22467 https://github.com/hackoregon/civic-devops/issues/261 Mozilla/5.0 (Macintosh; Intel Mac OS X 10.14; rv:69.0) Gecko/20100101 Firefox/69.0 0.192387
10.180.12.108 [29/Sep/2019:01:30:05 +0000] GET /housing-affordability/ HTTP/1.1 200 19859 - ELB-HealthChecker/2.0 0.011367