Initial exercise setup.

Additions

* Instructions for manually starting the database.
* Each phase now has a success criteria with how to verify.
* Troubleshooting section for working with the Docker DB container.
* All phases of the exercise are described in README.md (with as little advanced hints as possible).
* DFD to illustrate phase 1
* Debugging starts the database container and applies schema migrations (no setup required).
* Launch settings for VS Code, VS 2022 and Rider (IntelliJ IDEA).
* Swagger UI is available at <http://localhost:8080/swagger/index.html> for testing.

service/Properties/launchSettings.json

@@ -0,0 +1,14 @@
+{
+  "profiles": {
+    "service": {
+      "commandName": "Project",
+      "launchBrowser": true,
+      "useSSL": false,
+      "launchUrl": "http://localhost:8080/swagger/index.html",
+      "applicationUrl": "http://localhost:8080/swagger/index.html",
+      "environmentVariables": {
+        "ASPNETCORE_ENVIRONMENT": "Development"
+      },
+    }
+  }
+}