chore: track terraform modules in telemetry (#15450)

Addresses https://github.com/coder/nexus/issues/35.

This PR:

- Adds a `workspace_modules` table to track modules used by the
Terraform provisioner in provisioner jobs.
- Adds a `module_path` column to the `workspace_resources` table,
allowing to identify which module a resource originates from.
- Starts pushing this new information into telemetry.

For the person reviewing this PR, do not fret about the 1,500 new lines
- ~1,000 of them are auto-generated.

provisioner/terraform/modules.go

@@ -0,0 +1,64 @@
+package terraform
+
+import (
+	"encoding/json"
+	"os"
+	"path/filepath"
+
+	"golang.org/x/xerrors"
+
+	"github.com/coder/coder/v2/provisionersdk/proto"
+)
+
+type module struct {
+	Source  string `json:"Source"`
+	Version string `json:"Version"`
+	Key     string `json:"Key"`
+}
+
+type modulesFile struct {
+	Modules []*module `json:"Modules"`
+}
+
+func getModulesFilePath(workdir string) string {
+	return filepath.Join(workdir, ".terraform", "modules", "modules.json")
+}
+
+func parseModulesFile(filePath string) ([]*proto.Module, error) {
+	modules := &modulesFile{}
+	data, err := os.ReadFile(filePath)
+	if err != nil {
+		return nil, xerrors.Errorf("read modules file: %w", err)
+	}
+	if err := json.Unmarshal(data, modules); err != nil {
+		return nil, xerrors.Errorf("unmarshal modules file: %w", err)
+	}
+	protoModules := make([]*proto.Module, len(modules.Modules))
+	for i, m := range modules.Modules {
+		protoModules[i] = &proto.Module{Source: m.Source, Version: m.Version, Key: m.Key}
+	}
+	return protoModules, nil
+}
+
+// getModules returns the modules from the modules file if it exists.
+// It returns nil if the file does not exist.
+// Modules become available after terraform init.
+func getModules(workdir string) ([]*proto.Module, error) {
+	filePath := getModulesFilePath(workdir)
+	if _, err := os.Stat(filePath); os.IsNotExist(err) {
+		return nil, nil
+	}
+	modules, err := parseModulesFile(filePath)
+	if err != nil {
+		return nil, xerrors.Errorf("parse modules file: %w", err)
+	}
+	filteredModules := []*proto.Module{}
+	for _, m := range modules {
+		// Empty string means root module. It's always present, so we skip it.
+		if m.Source == "" {
+			continue
+		}
+		filteredModules = append(filteredModules, m)
+	}
+	return filteredModules, nil
+}