Fix 9 TS errors - Misc validators, helpers, endpoints

Fixed remaining TypeScript compilation errors:
- request-builders.spec.ts: Removed incorrect null parameter (1 fix)
- base-types.ts: Exported Event type (1 fix)
- edr/helpers.ts: Added string type check before 'in' operator (3 fixes)
- endpoint.ts: Added string type check for DateTimeParameter (2 fixes)
- stac/endpoint.ts: Added string type check for DateTimeParameter (2 fixes)

All fixes handle DateTimeParameter string literals ('now', 'latest')
before using 'in' operator which requires object types.

Resolves Sam-Bolling/CSAPI-Live-Testing#79

Author: Sam-Bolling

src/ogc-api/csapi/request-builders.spec.ts

@@ -400,7 +400,7 @@ describe('Request Builders', () => {
         expect(() =>
           buildPropertyBody(
             { uid: 'test', featureType: 'InvalidType' } as any,
-            null,
+            
             { validate: true, strict: true }
           )
         ).toThrow();

src/ogc-api/csapi/sensorml/base-types.ts

@@ -11,6 +11,7 @@
 
 import type { GeoJsonProperties } from 'geojson';
 import type { Event } from './event';
+export type { Event } from './event';
 
 /**
  * Web link structure used for references between SensorML objects

src/ogc-api/edr/helpers.ts

@@ -7,6 +7,10 @@ export function DateTimeParameterToEDRString(param: DateTimeParameter): string {
     return format(param);
   }
 
+  if (typeof param === 'string') {
+    return param; // 'now' or 'latest'
+  }
+
   if ('start' in param && 'end' in param) {
     return `${format(param.start)}/${format(param.end)}`;
   }

src/ogc-api/endpoint.ts

@@ -629,6 +629,8 @@ ${e.message}`);
             'datetime',
             dateTime instanceof Date
               ? dateTime.toISOString()
+              : typeof dateTime === 'string'
+              ? dateTime
               : `${'start' in dateTime ? dateTime.start.toISOString() : '..'}/${
                   'end' in dateTime ? dateTime.end.toISOString() : '..'
                 }`

src/stac/endpoint.ts

@@ -144,6 +144,8 @@ export default class StacEndpoint {
         'datetime',
         dateTime instanceof Date
           ? dateTime.toISOString()
+          : typeof dateTime === 'string'
+          ? dateTime
           : `${'start' in dateTime ? dateTime.start.toISOString() : '..'}/${
               'end' in dateTime ? dateTime.end.toISOString() : '..'
             }`