feat: Read params from file for template/workspace creation (#1541)

* Read params from file for template/workspace creation

* Use os.ReadFile

* Refactor reading params into a separate module

* Add comments and unit tests

* Rename variable

* Uncomment and fix unit test

* Fix comment

* Refactor tests

* Fix unit tests for windows

* Fix unit tests for Windows

* Add comments for the hotfix

cli/parameter.go

@@ -0,0 +1,56 @@
+package cli
+
+import (
+	"os"
+
+	"golang.org/x/xerrors"
+	"gopkg.in/yaml.v3"
+
+	"github.com/coder/coder/cli/cliui"
+	"github.com/coder/coder/codersdk"
+	"github.com/spf13/cobra"
+)
+
+// Reads a YAML file and populates a string -> string map.
+// Throws an error if the file name is empty.
+func createParameterMapFromFile(parameterFile string) (map[string]string, error) {
+	if parameterFile != "" {
+		parameterMap := make(map[string]string)
+
+		parameterFileContents, err := os.ReadFile(parameterFile)
+
+		if err != nil {
+			return nil, err
+		}
+
+		err = yaml.Unmarshal(parameterFileContents, &parameterMap)
+
+		if err != nil {
+			return nil, err
+		}
+
+		return parameterMap, nil
+	}
+
+	return nil, xerrors.Errorf("Parameter file name is not specified")
+}
+
+// Returns a parameter value from a given map, if the map exists, else takes input from the user.
+// Throws an error if the map exists but does not include a value for the parameter.
+func getParameterValueFromMapOrInput(cmd *cobra.Command, parameterMap map[string]string, parameterSchema codersdk.ParameterSchema) (string, error) {
+	var parameterValue string
+	if parameterMap != nil {
+		var ok bool
+		parameterValue, ok = parameterMap[parameterSchema.Name]
+		if !ok {
+			return "", xerrors.Errorf("Parameter value absent in parameter file for %q!", parameterSchema.Name)
+		}
+	} else {
+		var err error
+		parameterValue, err = cliui.ParameterSchema(cmd, parameterSchema)
+		if err != nil {
+			return "", err
+		}
+	}
+	return parameterValue, nil
+}