identity/oidc: fix duplicate keys in well-known

[jasonodonnell]

A bug was found where well-known keys would return duplicate entries when roles shared a key. This adds a check to ensure we haven't appended the keys already.

[fairclothjm]

Thanks!

[fairclothjm]

manual test looks good

#!/usr/bin/env bash
vault write identity/oidc/key/key1 rotation_period=2m verification_ttl=2m
vault write identity/oidc/role/role1 key=key1 ttl=1m
vault write identity/oidc/role/role2 key=key1 ttl=1m

curl -s \
  -X GET \
  http://127.0.0.1:8200/v1/identity/oidc/.well-known/keys \
  | jq -r ".keys[].kid"

Output:

Success! Data written to: identity/oidc/key/key1
Success! Data written to: identity/oidc/role/role1
Success! Data written to: identity/oidc/role/role2
34939e00-e875-943e-fea5-d03fd6c6953b
fa8c52f4-05f5-95b9-bffd-cd7fbc4acc25

[calvn]

One last comment, otherwise LGTM!

[calvn]

Small nit: can we move the declaration of jwks closer, maybe somewhere in here?

[austingebauer]

Good idea 👍 Done in d16505f.