feat(plugins): add HTTP host service (#5095)

* feat(httpclient): implement HttpClient service for outbound HTTP requests in plugins

Signed-off-by: Deluan <deluan@navidrome.org>

* feat(httpclient): enhance SSRF protection by validating host requests against private IPs

Signed-off-by: Deluan <deluan@navidrome.org>

* feat(httpclient): support DELETE requests with body in HttpClient service

Signed-off-by: Deluan <deluan@navidrome.org>

* feat(httpclient): refactor HTTP client initialization and enhance redirect handling

Signed-off-by: Deluan <deluan@navidrome.org>

* refactor(http): standardize naming conventions for HTTP types and methods

Signed-off-by: Deluan <deluan@navidrome.org>

* refactor example plugin to use host.HTTPSend for improved error management

Signed-off-by: Deluan <deluan@navidrome.org>

* fix(plugins): fix IPv6 SSRF bypass and wildcard host matching

Fix two bugs in the plugin HTTP/WebSocket host validation:

1. extractHostname now strips IPv6 brackets when no port is present
(e.g. "[::1]" → "::1"). Previously, net.SplitHostPort failed for
bracketed IPv6 without a port, leaving brackets intact. This caused
net.ParseIP to return nil, bypassing the private/loopback SSRF guard.

2. matchHostPattern now treats "*" as an allow-all pattern. Previously,
a bare "*" only matched via exact equality, so plugins declaring
requiredHosts: ["*"] (like webhook-rs) had all requests rejected.

---------

Signed-off-by: Deluan <deluan@navidrome.org>

plugins/pdk/go/host/doc.go

@@ -38,6 +38,7 @@ The following host services are available:
   - Artwork: provides artwork public URL generation capabilities for plugins.
   - Cache: provides in-memory TTL-based caching capabilities for plugins.
   - Config: provides access to plugin configuration values.
+  - HTTP: provides outbound HTTP request capabilities for plugins.
   - KVStore: provides persistent key-value storage for plugins.
   - Library: provides access to music library metadata for plugins.
   - Scheduler: provides task scheduling capabilities for plugins.