Replace social login with own user management

[skuzzle]

Given the fact that I do not want to allow external sites tracking my users, requiring a google account to enjoy all the features seems a little odd.

• It should be possible to create CMP native user accounts
• Google login should still work for those who don't care
• It should be possible to shift counters assigned to google accounts over to a native CMP account
• Maybe integrate furhter oauth providers like GitHub, Twitter ,..?

Open Todos:

• [x] Use JWT sub claim to report unique user id(=email) and use custom claim to report the user name
• [x] In swarm deployment, the authorization server is not reachabel via its public domain from within the frontend container. WTF?
• [ ] Configure authorization-server's client registration via properties. Allows to store client password as docker secret and to have feature specific redirect urls
• [x] Find a way to support multiple JWKS URI to support Google and CMP authorization server at the same time (Build custom JwtDecoder that tries multiple keys)
• [ ] User is logged out when access token is expired. Need to use the refresh token to renew login (See OAuth2AuthenticatedClientManager)
• [ ] Build workflow to assign counter from google to native cmp. Or maybe better: from one oauth provider to another
• [ ] Add issuer endpoint in auth server: https://tools.ietf.org/id/draft-ietf-oauth-discovery-08.html
• [ ] OAuth (frontend) client currently queries the user info endpoint though all information are allready contained in the token
• [ ] Maybe externalize token signing key instead of regenerating it on reboot?

[skuzzle]

Important links: Official OAuth Page: https://oauth.net/2/

https://docs.spring.io/spring-security-oauth2-boot/docs/current/reference/html5

https://spring.io/blog/2018/03/06/using-spring-security-5-to-integrate-with-oauth-2-secured-services-such-as-facebook-and-github

https://alexbilbie.com/guide-to-oauth-2-grants/

https://github.com/spring-projects/spring-security/blob/9f6af4f3b8e79a8a45369d99862cd3d96f4083ce/config/src/main/java/org/springframework/security/config/oauth2/client/CommonOAuth2Provider.java

[skuzzle]

Changed firewall from ufw to pure iptables. See https://www.digitalocean.com/community/tutorials/how-to-configure-the-linux-firewall-for-docker-swarm-on-ubuntu-16-04