Added adapter-cache-redis package

refs https://github.com/TryGhost/Toolbox/issues/515

- Redis-based caches can be used on hosted-environments to store information with high memory impact - when in-memory caches would be too impractical to use
- This is a placeholder package for a cluster-aware Redis cache implementation compatible with Ghost's cache adapter interface (a41d351f16/packages/adapter-base-cache)

ghost/adapter-cache-redis/.eslintrc.js

@@ -0,0 +1,6 @@
+module.exports = {
+    plugins: ['ghost'],
+    extends: [
+        'plugin:ghost/node'
+    ]
+};

ghost/adapter-cache-redis/README.md

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+# Adapter Cache Redis
+
+Redis based cache adapter with support of Redis cluster
+
+
+## Usage
+
+
+## Develop
+
+This is a monorepo package.
+
+Follow the instructions for the top-level repo.
+1. `git clone` this repo & `cd` into it as usual
+2. Run `yarn` to install top-level dependencies.
+
+
+
+## Test
+
+- `yarn lint` run just eslint
+- `yarn test` run lint and tests
+

ghost/adapter-cache-redis/index.js

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+module.exports = require('./lib/adapter-cache-redis');

ghost/adapter-cache-redis/package.json

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+{
+  "name": "@tryghost/adapter-cache-redis",
+  "version": "0.0.0",
+  "repository": "https://github.com/TryGhost/Ghost/tree/main/packages/adapter-cache-redis",
+  "author": "Ghost Foundation",
+  "private": true,
+  "main": "index.js",
+  "scripts": {
+    "dev": "echo \"Implement me!\"",
+    "test:unit": "NODE_ENV=testing c8 --all --check-coverage --100  --reporter text --reporter cobertura mocha './test/**/*.test.js'",
+    "test": "yarn test:unit",
+    "lint:code": "eslint *.js lib/ --ext .js --cache",
+    "lint": "yarn lint:code && yarn lint:test",
+    "lint:test": "eslint -c test/.eslintrc.js test/ --ext .js --cache"
+  },
+  "files": [
+    "index.js",
+    "lib"
+  ],
+  "devDependencies": {
+    "c8": "7.12.0",
+    "mocha": "10.2.0",
+    "sinon": "15.0.1"
+  },
+  "dependencies": {}
+}

ghost/adapter-cache-redis/test/.eslintrc.js

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+module.exports = {
+    plugins: ['ghost'],
+    extends: [
+        'plugin:ghost/test'
+    ]
+};

ghost/adapter-cache-redis/test/hello.test.js

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+const assert = require('assert');
+
+describe('Hello world', function () {
+    it('Runs a test', function () {
+        // TODO: Write me!
+        assert.ok(require('../index'));
+    });
+});