added code to migrate series provider default language from 2-code to 3-code

fixed "string indices must be integers" when attempting to retrieve series provider season images
fixed "cannot serialize (type int)" when attempting to write series metadata nfo

switched anonymous referrer to anonym.to
fixed local variable 'refresh_token' referenced before assignment in cache offline token migration

Added API login method for SiCKRAGE external API using new SSO API key
Removed SiCKRAGE SSO offline token usage in favour of SiCKRAGE SSO API key
Improved OAuth2 handling for external SiCKRAGE API
Added external series provider API support
Added migration code to convert lang column on tv_shows table to ISO639-3
Added migration code to convert offline token to apikey