Key-Value Storages (#674)

Fix lint

Add docs for keyvalue config options

Use keyvalue store to cache unsplash photo results

Cleanup

Use keyvalue store for upload avatar

Use keyvalue store for initials avatar

Fix initializing metrics

Use keyvalue for metrics

Add IncryBy and DecrBy methods to increase or decrease a value

Fix lint

Return custom error if a key does not exist

Init keyvalue storage

Follow the keyvalue storage setting for things like cache and other

Add docs

Add configuration of the storage backend

Add redis keyvalue storage implementation

Add doc comments

Add methods to use storage through the package itself

Add memory implementation for keyvalue store

Co-authored-by: kolaente <k@knt.li>
Reviewed-on: https://kolaente.dev/vikunja/api/pulls/674
Co-Authored-By: konrad <konrad@kola-entertainments.de>
Co-Committed-By: konrad <konrad@kola-entertainments.de>

pkg/red/redis.go

@@ -26,6 +26,10 @@ var r *redis.Client
 
 // InitRedis initializes a redis connection
 func InitRedis() {
+	if r != nil {
+		return
+	}
+
 	if !config.RedisEnabled.GetBool() {
 		return
 	}