Change authentication to token checked with OPA

[majst01]

Remove the default HMAC as well https://github.com/metal-stack/masterdata-api/blob/master/pkg/auth/hmacauther.go#L19

[majst01]

can be done after #122

[Gerrit91]

Do we actually need a token for the masterdata-api? It is not exposed and our other services usually do not offer token auth either.

[majst01]

right, closing