v2 release planning #286

Remove deprecated code

• The AI custom placeholder methods, upload_translation, and the Enterprise project-level report settings templates.
• The misspelled edit_applicatoin_installation, legacy report types, and translateUntranslatedOnly, splitFiles, glossaryAccess, preTranslationAiPromptId.
• Dead enum values: /url in the webhook patch paths, /shortcuts in AI settings, SPLIT_FILES, BundlePatchPath.DESCRIPTION, and the ScopeType.GRPOUP typo.
• The QA revalidation calls without revalidationId.

Make the API consistent

• Naming: use camelCase parameters everywhere. BranchesResource, StringCorrectionsResource, import_translations and the report methods still use project_id-style names.
• Project ID: make projectId optional, falling back to the client's project, on every project-scoped method.
• Branches: keep one implementation. The branch methods currently exist on both BranchesResource and SourceFilesResource.
• Argument order: move parameters that the API made optional (fileIds, languageIds, format, exportPattern, task fileIds/type) behind keyword-only arguments.
• Required fields: enforce fields the spec now requires, such as config when adding a field.
• Renames: rename preTranslationId to jobIdentifier, and turn ContributionMode into a real Enum.

Change the requester

• Nulls: stop stripping None from request bodies, or give callers a way to send null. Right now you can't clear a key-value TTL or store nulls in app data.
• Dates in query params: serialize them as ISO-8601. Today they go out with a space instead of T, and dates without a timezone crash.
• List params: comma-join lists, tuples and sets in one place instead of in each method.

Drop Python 3.8

• It is end-of-life. Dropping it would allow X | Y unions and the typing.TypedDict import directly.