Add custom parameter mapping when using custom API domain

[vincentsarago]

When using custom API domain in API Gateway the FastAPI application (starlette) will still receive the api gateway hostname and thus use it internally (e.g if you have an endpoint that construct other endpoint url, it will return the API gateway url instead of you custom domain name)

e.g titiler

import httpx

resp = httpx.get("https://stac.eoapi.dev")
print(resp.json()["links"][2]

>>      {
      "rel": "data",
      "type": "application/json",
      "href": "https://stac.eoapi.dev/collections"
    }

☝️ this is giving the correct result (stac.eoapi.dev hostname) because I've manually added custom parameter mapping in the API Gateway console:

I believe we can automatically create this in 👇

eoapi-cdk/lib/stac-api/index.ts

Lines 60 to 65 in a1081a2

	const stacApi = new HttpApi(this, `${Stack.of(this).stackName}-stac-api`, {
	defaultDomainMapping: props.stacApiDomainName ? {
	domainName: props.stacApiDomainName
	} : undefined,
	defaultIntegration: new HttpLambdaIntegration("integration", this.stacApiLambdaFunction),
	});

with:
https://constructs.dev/packages/@aws-cdk/aws-apigatewayv2/v/1.204.0/api/ParameterMapping?lang=typescript

    const stacApi = new HttpApi(this, `${Stack.of(this).stackName}-stac-api`, {
      defaultDomainMapping: props.stacApiDomainName ? { 
        domainName: props.stacApiDomainName
      } : undefined,
      defaultIntegration: new HttpLambdaIntegration("integration", this.stacApiLambdaFunction, parameterMapping = props.stacApiDomainName ? {new ParameterMapping().overwriteHeader('host', MappingValue.requestHeader(props.stacApiDomainName))} : undefined),
    });

[slesaad]

@vincentsarago i tested this with the ghg center backend, and MappingValue.requestHeader threw an error

Invalid mapping expression specified: Validation Result: warnings : [], errors : [Host header manipulation only supports overwriting and must be statically defined] (Service: AmazonApiGatewayV2; Status Code: 400; Error Code: BadRequestException; Request ID: 2e6e9902-e3c9-4fe7-8e22-3fbc4bee9d92; Proxy: null

should probably be custom instead

MappingValue.custom(props.stacApiDomainName)