Spire Integration

Nobody has claimed this yet.

## Feature Request

I'd love it if linkerd could obtain its cert/key pairs for mtls from spire

### What problem are you trying to solve?

spire provides a way to have trusted hardware with it's tpm node attestation which is, I think, fairly unique. It's also incredibly useful when you have a box in a field running kubernetes, you don't want someone swapping in their own, malicious box.

see https://github.com/bloomberg/spire-tpm-plugin

### How should the problem be solved?

I'd like to be able to configure linkerd to use the local spire-agent to request for certs/keys

### Any alternatives you've considered?

Currently envoy and istio support it, but I'd rather use linkerd if possible.

### How would users interact with this feature?

Not entirely sure yet, I'm only really starting to read up on linkerd

No source file, test, or entry point is identified in the issue. Start by mapping Linkerd's existing certificate/key configuration to the local SPIRE agent interface; define the user-facing configuration and mTLS success criteria before implementing, then verify certificate issuance and rotation in Kubernetes.

Written by the indexing model from the issue text.