default header value callback

* add new handler to set default values for header params

Author: Stefan Schubert

src/mustache/api.service.mustache

@@ -184,6 +184,9 @@ export class {{classname}} {
 {{/hasQueryParams}}
         let headers = {{#useHttpClient}}this.defaultHeaders;{{/useHttpClient}}{{^useHttpClient}}new Headers(this.defaultHeaders.toJSON()); // https://github.com/angular/angular/issues/6845{{/useHttpClient}}
 {{#headerParams}}
+        if(typeof this.configuration.defaultHeaderValue === 'function') {
+            {{paramName}} = this.configuration.defaultHeaderValue('{{paramName}}');
+        }
         {{#isListContainer}}
         if ({{paramName}}) {
             {{#useHttpClient}}headers = {{/useHttpClient}}headers.set('{{baseName}}', {{paramName}}.join(COLLECTION_FORMATS['{{collectionFormat}}']));

src/mustache/configuration.mustache

@@ -14,6 +14,7 @@ export interface ConfigurationParameters {
     password?: string;
     accessToken?: string | (() => string);
     errorHandler?: (err: any, operationName: string) => Observable<never>;
+    defaultHeaderValue?: (headerName: string) => string;
     basePath?: string;
     withCredentials?: boolean;
 }
@@ -24,6 +25,7 @@ export class Configuration {
     password?: string;
     accessToken?: string | (() => string);
     errorHandler?: (err: any, operationName: string) => Observable<never>;
+    defaultHeaderValue?: (headerName: string) => string;
     basePath?: string;
     withCredentials?: boolean;
 
@@ -33,6 +35,7 @@ export class Configuration {
         this.password = configurationParameters.password;
         this.accessToken = configurationParameters.accessToken;
         this.errorHandler = configurationParameters.errorHandler;
+        this.defaultHeaderValue = configurationParameters.defaultHeaderValue;
         this.basePath = configurationParameters.basePath;
         this.withCredentials = configurationParameters.withCredentials;
     }