message: refactor(compiler): clarify that message constructor takes a customId
  Previously the parameter was `id` which is ambigous because it
  could be a computed value rather than a developer specified custom
  value.
  PR Close
diff: @@ -21,7 +21,7 @@ const _expParser = new ExpressionParser(new ExpressionLexer());
  export type VisitNodeFn = (html: html.Node, i18n: i18n.Node) => i18n.Node;
  export interface I18nMessageFactory {
  - (nodes: html.Node[], meaning: string, description: string, id: string,
  + (nodes: html.Node[], meaning: string, description: string, customId: string,
  visitNodeFn?: VisitNodeFn): i18n.Message;
  }
  @@ -31,8 +31,8 @@ export interface I18nMessageFactory {
  export function createI18nMessageFactory(interpolationConfig: InterpolationConfig):
  I18nMessageFactory {
  const visitor = new _I18nVisitor(_expParser, interpolationConfig);
  - return (nodes, meaning, description, id, visitNodeFn) =>
  - visitor.toI18nMessage(nodes, meaning, description, id, visitNodeFn);
  + return (nodes, meaning, description, customId, visitNodeFn) =>
  + visitor.toI18nMessage(nodes, meaning, description, customId, visitNodeFn);
  }
  interface I18nMessageVisitorContext {
  @@ -54,7 +54,7 @@ class _I18nVisitor implements html.Visitor {
  private _interpolationConfig: InterpolationConfig) {}
  public toI18nMessage(
  - nodes: html.Node[], meaning: string, description: string, id: string,
  + nodes: html.Node[], meaning: string, description: string, customId: string,
  visitNodeFn: VisitNodeFn|undefined): i18n.Message {
  const context: I18nMessageVisitorContext = {
  isIcu: nodes.length == 1 && nodes[0] instanceof html.Expansion,
  @@ -69,7 +69,7 @@ class _I18nVisitor implements html.Visitor {
  return new i18n.Message(
  i18nodes, context.placeholderToContent, context.placeholderToMessage, meaning, description,
  - id);
  + customId);
  }
  visitElement(el: html.Element, context: I18nMessageVisitorContext): i18n.Node {
  