chore(all): review error wrappings

- remove repetitive `cannot` and `failed` prefixes
- rename `unmarshaling` to `decoding`

internal/openvpn/extract/data.go

@@ -17,12 +17,12 @@ func (e *Extractor) Data(filepath string) (lines []string,
 	connection models.Connection, err error) {
 	lines, err = readCustomConfigLines(filepath)
 	if err != nil {
-		return nil, connection, fmt.Errorf("cannot read configuration file: %w", err)
+		return nil, connection, fmt.Errorf("reading configuration file: %w", err)
 	}
 
 	connection, err = extractDataFromLines(lines)
 	if err != nil {
-		return nil, connection, fmt.Errorf("cannot extract connection from file: %w", err)
+		return nil, connection, fmt.Errorf("extracting connection from file: %w", err)
 	}
 
 	return lines, connection, nil

internal/openvpn/extract/extract.go

@@ -54,14 +54,14 @@ func extractDataFromLine(line string) (
 	case strings.HasPrefix(line, "proto "):
 		protocol, err = extractProto(line)
 		if err != nil {
-			return nil, 0, "", fmt.Errorf("failed extracting protocol from proto line: %w", err)
+			return nil, 0, "", fmt.Errorf("extracting protocol from proto line: %w", err)
 		}
 		return nil, 0, protocol, nil
 
 	case strings.HasPrefix(line, "remote "):
 		ip, port, protocol, err = extractRemote(line)
 		if err != nil {
-			return nil, 0, "", fmt.Errorf("failed extracting from remote line: %w", err)
+			return nil, 0, "", fmt.Errorf("extracting from remote line: %w", err)
 		}
 		return ip, port, protocol, nil
 	}

internal/openvpn/extract/extract_test.go

@@ -29,7 +29,7 @@ func Test_extractDataFromLines(t *testing.T) {
 		},
 		"extraction error": {
 			lines: []string{"bla bla", "proto bad", "remote 1.2.3.4 1194 tcp"},
-			err:   errors.New("on line 2: failed extracting protocol from proto line: network protocol not supported: bad"),
+			err:   errors.New("on line 2: extracting protocol from proto line: network protocol not supported: bad"),
 		},
 		"only use first values found": {
 			lines: []string{"proto udp", "proto tcp", "remote 1.2.3.4 443 tcp", "remote 5.2.3.4 1194 udp"},