[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>

go.mod

@@ -58,8 +58,6 @@ require (
 	github.com/muesli/smartcrop v0.3.0 // indirect
 	github.com/olekukonko/tablewriter v0.0.1 // indirect
 	github.com/olivere/elastic v6.2.23+incompatible // indirect
-	github.com/onsi/ginkgo v1.8.0 // indirect
-	github.com/onsi/gomega v1.5.0 // indirect
 	github.com/pborman/uuid v1.2.0
 	github.com/pelletier/go-toml v1.4.0 // indirect
 	github.com/pkg/errors v0.8.1