[MM 19840] Create a Cache Interface abstraction to support multiple cache backends (#13384)

* Refactor to use structured logging

* Properly formatted with gofmt

* created interface Cache, but construction of cache is still coupled.

* Implementing cache factories to build caches

* Simple redis implementation without error handling. Keys and values by default are string

* refactor NewLocalCacheLayer to inject cache factory

* Removed redis impl to focus on cache abstraction

* CacheFactory injected on sqlsupplier and saved in Store struct

* remove useless private method

* replace concrete declaration of lru cache to cache abstraction

* discard spaces

* Renamed factory to provider because concrete implementations of factories may hold an state (such as a redis client for example)

* refactor to include all caches in the same package cache and subpackages

* method close cache. This method will be used for concrete implementations that need to release resources (close a connection, etc)

* closing cacheprovider and releasing resources while closing sql store

* fixed merge conflict fail

* gofmt files

* remove unused property from post_store

* naming refactor to avoid stutter. Added godocs on interface

* Store doesnt know anything about the cache and provider. Cache provider will be built after loading config and injected in localCacheLayer

* fixed broken test

* cache provider initialized before RunOldAppInitialization which initializes the localcachelayer

* move statusCache to server to initialize it with the new cache provider

* update terms_service and channel_layer to have new cacheProvider

* gofmt

* Add Connect method to the cache provider

* mock cacheprovider in user_layer_test

Co-authored-by: Ben Schumacher <ben.schumacher@mattermost.com>
Co-authored-by: mattermod <mattermod@users.noreply.github.com>

store/sqlstore/channel_store.go

@@ -18,8 +18,8 @@ import (
 	"github.com/mattermost/mattermost-server/v5/einterfaces"
 	"github.com/mattermost/mattermost-server/v5/mlog"
 	"github.com/mattermost/mattermost-server/v5/model"
+	"github.com/mattermost/mattermost-server/v5/services/cache/lru"
 	"github.com/mattermost/mattermost-server/v5/store"
-	"github.com/mattermost/mattermost-server/v5/utils"
 )
 
 const (
@@ -274,9 +274,9 @@ type publicChannel struct {
 	Purpose     string `json:"purpose"`
 }
 
-var allChannelMembersForUserCache = utils.NewLru(ALL_CHANNEL_MEMBERS_FOR_USER_CACHE_SIZE)
-var allChannelMembersNotifyPropsForChannelCache = utils.NewLru(ALL_CHANNEL_MEMBERS_NOTIFY_PROPS_FOR_CHANNEL_CACHE_SIZE)
-var channelByNameCache = utils.NewLru(model.CHANNEL_CACHE_SIZE)
+var allChannelMembersForUserCache = lru.New(ALL_CHANNEL_MEMBERS_FOR_USER_CACHE_SIZE)
+var allChannelMembersNotifyPropsForChannelCache = lru.New(ALL_CHANNEL_MEMBERS_NOTIFY_PROPS_FOR_CHANNEL_CACHE_SIZE)
+var channelByNameCache = lru.New(model.CHANNEL_CACHE_SIZE)
 
 func (s SqlChannelStore) ClearCaches() {
 	allChannelMembersForUserCache.Purge()