docs: Allow AWS IAM SigV4 for SDS AuthN (#8067)
docs: Allow AWS IAM SigV4 for SDS AuthN (#8067)

Per #8042, update documentation to clarify authentication required for SDS connections, and add notes about credential types in use today.

Risk Level: Low
Testing: Previewed content layout using RST parser.
Docs Changes: See description.

Signed-off-by: Brian Celenza <868bb3beba5221ac167e47f82b9d9e525a77761b@gmail.com>
lyft/envoy,envoyproxy/envoy,istio/envoy,envoyproxy/envoy,jrajahalme/envoy,envoyproxy/envoy-wasm,jrajahalme/envoy,jrajahalme/envoy,eklitzke/envoy,lizan/envoy,envoyproxy/envoy,envoyproxy/envoy,istio/envoy,istio/envoy,lyft/envoy,envoyproxy/envoy-wasm,lizan/envoy,envoyproxy/envoy-wasm,lyft/envoy,jrajahalme/envoy,istio/envoy,eklitzke/envoy,envoyproxy/envoy-wasm,lyft/envoy,envoyproxy/envoy,envoyproxy/envoy-wasm,istio/envoy,envoyproxy/envoy,lyft/envoy,eklitzke/envoy,istio/envoy,envoyproxy/envoy,envoyproxy/envoy-wasm,eklitzke/envoy,envoyproxy/envoy,istio/envoy,envoyproxy/envoy-wasm,envoyproxy/envoy,envoyproxy/envoy,lizan/envoy,eklitzke/envoy,eklitzke/envoy,lizan/envoy,jrajahalme/envoy,envoyproxy/envoy,lizan/envoy,envoyproxy/envoy,jrajahalme/envoy,lizan/envoy,lyft/envoy