Allow GET requests to be cached privately for 5m

At the moment we monkey-patch the Ruby API client library to cache GET request
responses for 5 minutes. It was done this way originally as ASP.NET Core was
preventing us from setting `Cache-Control` headers on authenticated requests.
This no longer seems to be the case and the core team appear to be actively
working towards a less opinionated caching implementation.

Add a custom attribute for short term (5m), private response caching that is
safe to use on most GET responses. Applies it to:

- All /types endpoints
- All /privacy_policies endpoints
- GET /teaching_events endpoints (search and upcoming)

GetIntoTeachingApi/Attributes/PrivateShortTermResponseCacheAttribute.cs

@@ -0,0 +1,13 @@
+using Microsoft.AspNetCore.Mvc;
+
+namespace GetIntoTeachingApi.Attributes
+{
+    public class PrivateShortTermResponseCacheAttribute : ResponseCacheAttribute
+    {
+        public PrivateShortTermResponseCacheAttribute()
+        {
+            Location = ResponseCacheLocation.Client;
+            Duration = 300;
+        }
+    }
+}

GetIntoTeachingApi/Controllers/PrivacyPoliciesController.cs

@@ -11,7 +11,8 @@ namespace GetIntoTeachingApi.Controllers
 {
     [Route("api/privacy_policies")]
     [ApiController]
-    [LogRequests]
+    [LogRequests]
+    [PrivateShortTermResponseCache]
     [Authorize]
     public class PrivacyPoliciesController : ControllerBase
     {

GetIntoTeachingApi/Controllers/TeachingEventsController.cs

@@ -15,7 +15,7 @@ namespace GetIntoTeachingApi.Controllers
 {
     [Route("api/teaching_events")]
     [ApiController]
-    [LogRequests]
+    [LogRequests]
     [Authorize]
     public class TeachingEventsController : ControllerBase
     {
@@ -40,7 +40,8 @@ public TeachingEventsController(
         }
 
         [HttpGet]
-        [CrmETag]
+        [CrmETag]
+        [PrivateShortTermResponseCache]
         [Route("search_indexed_by_type")]
         [SwaggerOperation(
             Summary = "Searches for teaching events, returning grouped by type.",
@@ -68,7 +69,8 @@ public async Task<IActionResult> SearchIndexedByType(
         }
 
         [HttpGet]
-        [CrmETag]
+        [CrmETag]
+        [PrivateShortTermResponseCache]
         [Route("upcoming_indexed_by_type")]
         [SwaggerOperation(
             Summary = "Retrieves upcoming teaching events grouped by type.",
@@ -83,7 +85,8 @@ public async Task<IActionResult> SearchIndexedByType(
         }
 
         [HttpGet]
-        [CrmETag]
+        [CrmETag]
+        [PrivateShortTermResponseCache]
         [Route("{readableId}")]
         [SwaggerOperation(
             Summary = "Retrieves an event.",

GetIntoTeachingApi/Controllers/TypesController.cs

@@ -13,7 +13,8 @@ namespace GetIntoTeachingApi.Controllers
 {
     [Route("api/types")]
     [ApiController]
-    [LogRequests]
+    [LogRequests]
+    [PrivateShortTermResponseCache]
     [Authorize]
     public class TypesController : ControllerBase
     {

GetIntoTeachingApiTests/Attributes/PrivateShortTermResponseCacheAttributeTests.cs

@@ -0,0 +1,19 @@
+using FluentAssertions;
+using GetIntoTeachingApi.Attributes;
+using Microsoft.AspNetCore.Mvc;
+using Xunit;
+
+namespace GetIntoTeachingApiTests.Attributes
+{
+    public class PrivateShortTermResponseCacheAttributeTests
+    {
+        [Fact]
+        public void Constructor_CorrectlySetsCacheControl()
+        {
+            var cache = new PrivateShortTermResponseCacheAttribute();
+
+            cache.Location.Should().Be(ResponseCacheLocation.Client);
+            cache.Duration.Should().Be(300);
+        }
+    }
+}

GetIntoTeachingApiTests/Controllers/PrivacyPoliciesControllerTests.cs

@@ -33,6 +33,12 @@ public void Authorize_IsPresent()
         public void LogRequests_IsPresent()
         {
             typeof(PrivacyPoliciesController).Should().BeDecoratedWith<LogRequestsAttribute>();
+        }
+
+        [Fact]
+        public void PrivateShortTermResponseCache_IsPresent()
+        {
+            typeof(PrivacyPoliciesController).Should().BeDecoratedWith<PrivateShortTermResponseCacheAttribute>();
         }
 
         [Fact]

GetIntoTeachingApiTests/Controllers/TeachingEventsControllerTests.cs

@@ -63,6 +63,15 @@ public void CrmETag_IsPresent()
             methods.ForEach(m => typeof(TeachingEventsController).GetMethod(m).Should().BeDecoratedWith<CrmETagAttribute>());
         }
 
+        [Fact]
+        public void CrmETagPrivateShortTermResponseCache_IsPresent()
+        {
+            JobStorage.Current = new Mock<JobStorage>().Object;
+            var methods = new[] { "Get", "SearchIndexedByType", "UpcomingIndexedByType" };
+
+            methods.ForEach(m => typeof(TeachingEventsController).GetMethod(m).Should().BeDecoratedWith<PrivateShortTermResponseCacheAttribute>());
+        }
+
         [Fact]
         public void AddAttendee_InvalidRequest_RespondsWithValidationErrors()
         {

GetIntoTeachingApiTests/Controllers/TypesControllerTests.cs

@@ -38,6 +38,12 @@ public void Authorize_IsPresent()
         public void LogRequests_IsPresent()
         {
             typeof(TypesController).Should().BeDecoratedWith<LogRequestsAttribute>();
+        }
+
+        [Fact]
+        public void PrivateShortTermResponseCache_IsPresent()
+        {
+            typeof(TypesController).Should().BeDecoratedWith<PrivateShortTermResponseCacheAttribute>();
         }
 
         [Fact]