Fix OpenAPI format for date/datetime/time/uuid/byte types across all data sources

[Copilot]

Why make this change?

• Closes [Bug]: OpenAPI and $filter for dates #2783
• DAB's generated OpenAPI document exposed all date, datetime2, datetimeoffset, uniqueidentifier, and binary columns as type: "string" with format: "" (empty). Clients dynamically building $filter expressions had no machine-readable signal to distinguish a date field from a plain string, forcing fragile heuristics.

What is this change?

New TypeHelper.GetOpenApiFormatFromSystemType(Type, DbType?)

Maps each supported CLR type + DbType to the correct OAS 3.0 format:

CLR type	DbType	OpenAPI format	Example DB types
DateTime	DbType.Date	date	MSSQL date
DateTime	anything else / null	date-time	MSSQL datetime/datetime2/smalldatetime, PostgreSQL timestamp, MySQL datetime
DateOnly	—	date	PostgreSQL date (Npgsql 8), MySQL DATE (MySqlConnector 2+)
DateTimeOffset	—	date-time	MSSQL datetimeoffset, PostgreSQL timestamptz
TimeOnly / TimeSpan	—	time	All databases' time columns
Guid	—	uuid	MSSQL uniqueidentifier, PostgreSQL uuid
byte[]	—	byte	binary/bytea columns
all other types	—	(null — field omitted)	int, string, bool, …

OpenApiDocumentor — both CreateComponentSchema (entity columns) and CreateSpRequestComponentSchema (stored procedure parameters) now call GetOpenApiFormatFromSystemType to populate the format field. format is null (omitted) when no standard format applies, eliminating the spurious format: "" shown in the bug report.

DateOnly cross-database support

Npgsql 8 and MySqlConnector 2+ report System.DateOnly as the CLR type for date columns. Without explicit entries in DAB's type maps this caused JsonDataType.Undefined in the OpenAPI path and would throw in the GraphQL/OData paths:

• Added typeof(DateOnly) → JsonDataType.String to _systemTypeToJsonDataTypeMap
• Added typeof(DateOnly) → DbType.Date to _systemTypeToDbTypeMap
• Added "DateOnly" => EdmPrimitiveTypeKind.Date to GetEdmPrimitiveTypeFromSystemType (OData $filter on date columns)
• Added "DateOnly" => DATETIME_TYPE to SchemaConverter.GetGraphQLTypeFromSystemType (prevents GraphQL startup failure)

How was this tested?

• Integration Tests
• Unit Tests — GetOpenApiFormatFromSystemType_ReturnsExpectedFormat: 13 data-driven cases covering every database / CLR-type / DbType combination; ResolveUnderlyingTypeForNullableValueType extended with DateOnly?

Sample Request(s)

After this fix, a datetime2 column like START_DATE_INCIDENT is described in the OpenAPI document as:

START_DATE_INCIDENT:
  type: string
  format: date-time   # was: format: ""

Clients can now detect date fields via format and correctly omit quotes in $filter:

GET /api/Incidents?$filter=START_DATE_INCIDENT ge 2025-01-01T00:00:00Z