message: api style: repeated field guidance
diff: @@ -71,6 +71,16 @@ In addition, the following conventions should be followed:
  * Always use plural field names for `repeated` fields, such as `filters`.
  +* Due to the fact that we consider JSON/YAML to be first class inputs, we cannot easily change a
  + a singular field to a repeated field (both due to JSON/YAML array structural differences as well
  + as singular vs. plural field naming). If there is a reasonable expectation that a field may need
  + to be repeated in the future, but we don't need it to be repeated right away, consider making it
  + repeated now but using constraints to enforce a maximum repeated size of 1. E.g.:
  +
  + ```proto
  + repeated OutputSink sinks = 1 [(validate.rules).repeated = {min_items: 1, max_items: 1}];
  + ```
  +
  * Always use upper camel case names for message types and enum types without embedded
  acronyms, such as `HttpRequest`.
  