FINERACT-2291: New command processing - create group

[nidhiii128]

Description

Migrates the "create group" REST endpoint (POST /v1/groups) from the legacy JSON-blob command-processing path to the new typed fineract-command framework.

Scope (PR 1 of 3 for FINERACT-2291)

• New typed GroupCreateRequest / GroupCreateResponse POJOs with Jakarta Validation (@NotBlank, @NotNull, @Size, @Positive, @AssertTrue for conditional activation date)
• New typed DatatableEntry POJO for the datatables field (with @Valid cascade and @NotBlank on registeredTableName)
• Date fields use String + manual parsing inside the impl (honoring request dateFormat and locale) to match Fineract's existing date-handling convention
• New GroupCreateCommand and GroupCreateCommandHandler using CommandHandler<REQ, RES>
• GroupingTypesWritePlatformService gets a new typed createGroup(GroupCreateRequest) overload (legacy createGroup(Long, JsonCommand) kept since other endpoints still use it)
• Controller POST /v1/groups now routes through CommandDispatcher
• AntMatcher added in SecurityConfig for POST /api/*/groups with CREATE_GROUP permission
• Resilience4j configuration added for commandGroupCreate in application.properties
• 9 translation keys added to ValidationMessages.properties
• Legacy CreateGroupCommandHandler deleted

Not in this PR (follow-up)

• accountNo user-supplied override field -> currently auto-generated only
• collectionMeetingCalendar field -> needs typed structure
• Update / Delete / Activate / Close / Membership / Staff endpoints -> separate follow-up PRs

Checklist

Please make sure these boxes are checked before submitting your pull request - thanks!

• Write the commit message as per our guidelines
• Acknowledge that we will not review PRs that are not passing the build ("green") - it is your responsibility to get a proposed PR to pass the build, not primarily the project's maintainers.
• Create/update unit or integration tests for verifying the changes made.
• Follow our coding conventions.
• Add required Swagger annotation and update API documentation at fineract-provider/src/main/resources/static/legacy-docs/apiLive.htm with details of any API changes
• This PR must not be a "code dump". Large changes can be made in a branch, with assistance. Ask for help on the developer mailing list.

Your assigned reviewer(s) will follow our guidelines for code reviews.