HTTP 500 error when relay failed to fetch user's pubk handle.

[perillamint]

When the Pleroma/Akkoma instance tries to add relay on their system and

• Pleroma/Akkoma instance does not have their relay actor activated
• The relay configured to validate signature (I'm not sure about it, not tested yet)

The server errors out 500.

Needs to reproduce this error in the lab environment and find out the bug

[perillamint]

Some relevant notes: relay_1 | 2022-12-15T03:01:48.862120Z ERROR tracing_actix_web::middleware: Error encountered while processing the incoming HTTP request: Status("https://[DATA EXPUNGED]/relay#main-key", 404)

[perillamint]

Found out the reason and updated issue

[perillamint]

Some cases may involve non-mutual follow of relay actor.

Some idea should be brought up to handle such cases. Related epic: #3

[perillamint]

User removal also AFFECTED by this issue. Need to be addressed ASAP.

Relavent logs:

relay_1  | 2022-12-19T06:14:55.681854Z  WARN relay::requests: Response from https://[REDACTED]/users/[REDACTED]#main-key, {"error":"Gone"}
relay_1  | 2022-12-19T06:14:55.682079Z ERROR tracing_actix_web::middleware: Error encountered while processing the incoming HTTP request: Status("https://[REDACTED]/users/[REDACTED]#main-key", 410)

[perillamint]

Signature checking must be relaxed in some cases. especially, user DELETE handle.

[perillamint]

Partially resolved (at least, not 500) in #9, but it must be discussed with @asonix to properly address and implement fix for it.

[perillamint]

Current implementation pitfalls:

• Since this PR using dummy actor which references example.com, it ALWAYS sends back message to its source instance

[perillamint]

Resolved in upstream, merged it back.