fix user cache misses for mixed-case username and email lookups

getUserByUsername/getUserByEmail normalize to lowercase before the
cache lookup, but the cache comparators matched case-sensitively, so a
mixed-case stored username never cache-hit and every login ran an
unindexed LOWER() scan. Compare case-insensitively inside the cache.

server/models/User.js

@@ -18,12 +18,16 @@ class UserCache {
   }
 
   getByEmail(email) {
-    const user = this.cache.find((u) => u.email === email)
+    if (!email) return null
+    const normalizedEmail = email.toLowerCase()
+    const user = this.cache.find((u) => u.email && u.email.toLowerCase() === normalizedEmail)
     return user
   }
 
   getByUsername(username) {
-    const user = this.cache.find((u) => u.username === username)
+    if (!username) return null
+    const normalizedUsername = username.toLowerCase()
+    const user = this.cache.find((u) => u.username && u.username.toLowerCase() === normalizedUsername)
     return user
   }
 

test/server/models/User.test.js

@@ -43,6 +43,38 @@ describe('User model', () => {
       expect(options.where.attribute.args[0].col).to.equal('email')
       expect(options.where.logic).to.equal('example.user@example.com')
     })
+
+    it('should hit the user cache for mixed-case username lookups', async () => {
+      User.sequelize = {
+        models: {
+          mediaProgress: {}
+        }
+      }
+      const cachedUser = { id: 'cache-test-user-1', username: 'CacheTestUser', email: 'cachetest@example.com', extraData: {} }
+      const findOneStub = sinon.stub(User, 'findOne').resolves(cachedUser)
+
+      await User.getUserByUsername('CacheTestUser')
+      await User.getUserByUsername('cachetestuser')
+      await User.getUserByUsername('CACHETESTUSER')
+
+      expect(findOneStub.callCount).to.equal(1)
+    })
+
+    it('should hit the user cache for mixed-case email lookups', async () => {
+      User.sequelize = {
+        models: {
+          mediaProgress: {}
+        }
+      }
+      const cachedUser = { id: 'cache-test-user-2', username: 'CacheEmailUser', email: 'CacheMail@Example.com', extraData: {} }
+      const findOneStub = sinon.stub(User, 'findOne').resolves(cachedUser)
+
+      await User.getUserByEmail('CacheMail@Example.com')
+      await User.getUserByEmail('cachemail@example.com')
+      await User.getUserByEmail('CACHEMAIL@EXAMPLE.COM')
+
+      expect(findOneStub.callCount).to.equal(1)
+    })
   })
 
   describe('getUserByIdOrOldId', () => {