refactor(probeservices): use httpclientx for check-in (#1580)

Closes ooni/probe#2724.

While there (1) make sure we test the check-in API call writes into the
kvstore as a side effect; (2) remove parts of ooapi that have now become
unused due to the change inside this pull request.

internal/checkincache/checkincache.go

@@ -10,8 +10,8 @@ import (
 	"github.com/ooni/probe-cli/v3/internal/runtimex"
 )
 
-// checkInFlagsState is the state created by check-in flags.
-const checkInFlagsState = "checkinflags.state"
+// CheckInFlagsState is the state created by check-in flags.
+const CheckInFlagsState = "checkinflags.state"
 
 // checkInFlagsWrapper is the struct wrapping the check-in flags.
 //
@@ -37,13 +37,13 @@ func Store(kvStore model.KeyValueStore, resp *model.OOAPICheckInResult) error {
 	}
 	data, err := json.Marshal(wrapper)
 	runtimex.PanicOnError(err, "json.Marshal unexpectedly failed")
-	return kvStore.Set(checkInFlagsState, data)
+	return kvStore.Set(CheckInFlagsState, data)
 }
 
 // GetFeatureFlag returns the value of a check-in feature flag. In case of any
 // error this function will always return a false value.
 func GetFeatureFlag(kvStore model.KeyValueStore, name string) bool {
-	data, err := kvStore.Get(checkInFlagsState)
+	data, err := kvStore.Get(CheckInFlagsState)
 	if err != nil {
 		return false // as documented
 	}

internal/checkincache/checkincache_test.go

@@ -28,7 +28,7 @@ func TestStore(t *testing.T) {
 			t.Fatal(err)
 		}
 		var wrapper checkInFlagsWrapper
-		data, err := memstore.Get(checkInFlagsState)
+		data, err := memstore.Get(CheckInFlagsState)
 		if err != nil {
 			t.Fatal(err)
 		}

internal/probeservices/checkin.go

@@ -4,9 +4,9 @@ import (
 	"context"
 
 	"github.com/ooni/probe-cli/v3/internal/checkincache"
-	"github.com/ooni/probe-cli/v3/internal/httpapi"
+	"github.com/ooni/probe-cli/v3/internal/httpclientx"
 	"github.com/ooni/probe-cli/v3/internal/model"
-	"github.com/ooni/probe-cli/v3/internal/ooapi"
+	"github.com/ooni/probe-cli/v3/internal/urlx"
 )
 
 // CheckIn function is called by probes asking if there are tests to be run
@@ -17,17 +17,31 @@ import (
 // or an explanatory error, in case of failure.
 func (c Client) CheckIn(
 	ctx context.Context, config model.OOAPICheckInConfig) (*model.OOAPICheckInResult, error) {
-	// prepare endpoint and descriptor for the API call
-	epnt := c.newHTTPAPIEndpoint()
-	desc := ooapi.NewDescriptorCheckIn(&config)
+	// construct the URL to use
+	URL, err := urlx.ResolveReference(c.BaseURL, "/api/v1/check-in", "")
+	if err != nil {
+		return nil, err
+	}
+
+	// issue the API call
+	resp, err := httpclientx.PostJSON[*model.OOAPICheckInConfig, *model.OOAPICheckInResult](
+		ctx, URL, &config, &httpclientx.Config{
+			Authorization: "", // not needed
+			Client:        c.HTTPClient,
+			Host:          c.Host,
+			Logger:        c.Logger,
+			UserAgent:     c.UserAgent,
+		})
 
-	// issue the API call and handle failures
-	resp, err := httpapi.Call(ctx, desc, epnt)
+	// handle the case of error
 	if err != nil {
 		return nil, err
 	}
 
-	// make sure we track selected parts of the response
+	// make sure we track selected parts of the response and ignore
+	// the error because OONI Probe would also work without this caching
+	// it would only work more poorly, but it does not seem worth it
+	// crippling it entirely if we cannot write into the kvstore
 	_ = checkincache.Store(c.KVStore, resp)
 	return resp, nil
 }