Add BrowserFeatureSupportEvents table (#865)

This table logs when any browser is released. Then it records whether or
not that the feature is supported. This is useful because the missing
one implementation calculation occurs when another browser is released
and not the target browser itself.

Fixes: #833

infra/storage/spanner/migrations/000010.sql

@@ -0,0 +1,37 @@
+-- Copyright 2024 Google LLC
+--
+-- Licensed under the Apache License, Version 2.0 (the "License");
+-- you may not use this file except in compliance with the License.
+-- You may obtain a copy of the License at
+--
+--     http://www.apache.org/licenses/LICENSE-2.0
+--
+-- Unless required by applicable law or agreed to in writing, software
+-- distributed under the License is distributed on an "AS IS" BASIS,
+-- WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+-- See the License for the specific language governing permissions and
+-- limitations under the License.
+
+-- This table provides an exhaustive view of feature support events for each browser,
+-- considering the releases of ALL browsers.
+-- It differs from BrowserFeatureAvailabilities, which only lists features explicitly
+-- mentioned as supported in a specific release.
+--
+-- TargetBrowserName: The browser for which we're tracking feature support.
+-- EventBrowserName: The browser whose release potentially affects the support status.
+-- EventReleaseDate: The release date of the EventBrowserName.
+--
+-- This structure is necessary due to the lack of full support for window functions
+-- in Spanner. It allows for efficient querying and analysis of "missing one
+-- implementation" counts and other feature-related metrics, considering the
+-- impact of releases from any browser, without relying on complex or
+-- potentially inefficient queries.
+CREATE TABLE IF NOT EXISTS BrowserFeatureSupportEvents (
+    TargetBrowserName STRING(64) NOT NULL,  -- The browser for which we're tracking support
+    EventBrowserName  STRING(64) NOT NULL,  -- The browser whose release triggered the event
+    EventReleaseDate TIMESTAMP NOT NULL,  -- The release date of the EventBrowserName
+    WebFeatureID      STRING(36) NOT NULL,
+    SupportStatus     STRING(32) NOT NULL, -- Check lib/gcpspanner/browser_feature_support_event.go for possible values.
+    CONSTRAINT FK_WebFeatureID FOREIGN KEY (WebFeatureID) REFERENCES WebFeatures(ID) ON DELETE CASCADE,
+    CONSTRAINT FK_EventBrowserRelease FOREIGN KEY (EventBrowserName, EventReleaseDate) REFERENCES BrowserReleases(BrowserName, ReleaseDate) ON DELETE CASCADE
+) PRIMARY KEY (TargetBrowserName, EventBrowserName, EventReleaseDate, WebFeatureID);