Initial commit

CalDAV and CardDAV checkers sharing a single Go module. Discovery follows
RFC 6764 (/.well-known + SRV/TXT), authenticated probes cover principal,
home-set, collections and a minimal REPORT query on top of go-webdav.
Common shape in internal/dav/; CalDAV adds a scheduling rule.

Surfaces its context URL (and each secure-SRV target) as TLS endpoints via
the EndpointDiscoverer interface, so the dedicated TLS checker can pick
them up without re-parsing observations.

HTML report foregrounds common misconfigs (well-known returning 200,
missing SRV, plaintext-only SRV, missing DAV capability, skipped auth
phase) as action-item callouts before the full phase breakdown.

Makefile

@@ -0,0 +1,37 @@
+CHECKER_VERSION ?= custom-build
+GO_LDFLAGS := -X main.Version=$(CHECKER_VERSION)
+
+BINARIES := checker-caldav checker-carddav
+PLUGINS := $(addsuffix .so,$(BINARIES))
+
+.PHONY: all test clean plugin docker docker-caldav docker-carddav $(BINARIES)
+
+all: $(BINARIES)
+
+checker-caldav:
+	go build -ldflags "$(GO_LDFLAGS)" -o $@ ./cmd/checker-caldav
+
+checker-carddav:
+	go build -ldflags "$(GO_LDFLAGS)" -o $@ ./cmd/checker-carddav
+
+plugin: $(PLUGINS)
+
+checker-caldav.so:
+	go build -buildmode=plugin -ldflags "$(GO_LDFLAGS)" -o $@ ./plugin/caldav
+
+checker-carddav.so:
+	go build -buildmode=plugin -ldflags "$(GO_LDFLAGS)" -o $@ ./plugin/carddav
+
+test:
+	go test ./...
+
+docker: docker-caldav docker-carddav
+
+docker-caldav:
+	docker build --build-arg TARGET=checker-caldav --build-arg CHECKER_VERSION=$(CHECKER_VERSION) -t happydomain/checker-caldav .
+
+docker-carddav:
+	docker build --build-arg TARGET=checker-carddav --build-arg CHECKER_VERSION=$(CHECKER_VERSION) -t happydomain/checker-carddav .
+
+clean:
+	rm -f $(BINARIES) $(PLUGINS)