2.2.1: encode CiString character set and forbid empty `tariff_id` in parameters/schemas

[juherr]

Summary

The 2.2.1 OpenAPI constrains identifier length but not the character set that the normative OCPI types mandate, and the tariff_id path parameter permits an empty value. As a result, values the prose spec forbids still validate against the OpenAPI.

Normative references

• types.asciidoc — CiString: "Case Insensitive String. Only printable ASCII allowed. (Non-printable characters like: Carriage returns, Tabs, Line breaks, etc are not allowed)"
• mod_tariffs.asciidoc — Tariff object: country_code = CiString(2), party_id = CiString(3), id = CiString(36).

Gaps in the current OpenAPI

1. CiString character set is not encoded. country_code / party_id are declared as (components/parameters.yaml, modules/tariffs/schema.yaml):

type: string
minLength: 2   # 3 for party_id
maxLength: 2   # 3 for party_id

type: string is case-sensitive UTF-8 with no charset restriction, so e.g. "é" or a value containing a line break validates — although CiString allows only printable ASCII. This applies to every CiString-typed field, not just these two.

2. tariff_id path parameter allows an empty value (modules/tariffs/parameters.yaml):

TariffIdParameter:
  in: path
  name: tariff_id
  schema:
    type: string
    maxLength: 36      # no minLength -> "" is valid

An empty tariff_id is unusable as a path segment in GET/PUT/DELETE /tariffs/{country_code}/{party_id}/{tariff_id}.

Suggested fix

• Add a pattern encoding the CiString rule (printable ASCII, no control characters), e.g. ^[\x20-\x7E]*$, to CiString-typed fields — at least to the common identifiers (country_code, party_id, id, tariff_id). The pattern must stay case-insensitive (CiString), so no [A-Z]-only regex.
• Add minLength: 1 to TariffIdParameter (and consider Tariff.id).

Relation to existing issues

Continues the OpenAPI↔prose fidelity work in #5 (date regex), #10 (id length), #11 (currency minLength). Those did not cover the CiString character set nor the parameter layer.