fix(oas): parse headers as case insensitve

Header name fields were not being handled as case-insensitive,
which would cause unwanted authentication and validation errors.
Refer RFC7230.

Fixes exegesis-js#75

src/oas3/Operation.ts

@@ -8,7 +8,7 @@ import { contentToRequestMediaTypeRegistry } from './oasUtils';
 import RequestMediaType from './RequestMediaType';
 import Oas3CompileContext from './Oas3CompileContext';
 import Parameter from './Parameter';
-import { RawValues, parseParameterGroup, parseQueryParameters } from './parameterParsers';
+import { RawValues, parseParameterGroup, parseQueryParameters, parseHeaderParameters } from './parameterParsers';
 import {
     ParametersMap,
     ParametersByLocation,
@@ -211,7 +211,7 @@ export default class Operation {
 
         return {
             query: parseQueryParameters(this._parameters.query, queryString),
-            header: parseParameterGroup(this._parameters.header, headers || {}),
+            header: parseHeaderParameters(this._parameters.header, headers || {}),
             server: params.serverParams || {},
             path: rawPathParams ? parseParameterGroup(this._parameters.path, rawPathParams) : {},
             cookie: {}

src/oas3/parameterParsers/index.ts

@@ -188,3 +188,17 @@ export function parseQueryParameters(
     const rawValues = querystring.parse(query || '', '&', '=', {decodeURIComponent: (val: string) => val});
     return _parseParameterGroup(params, rawValues, query || '');
 }
+
+export function parseHeaderParameters(
+    params: {
+        location: ParameterLocation,
+        parser: ParameterParser
+    }[],
+    rawHeaders: RawValues
+) {
+    const rawValues = ld.mapKeys(
+        rawHeaders,
+        (_value: string | string[] | undefined, key: string) => key.toLowerCase()
+    );
+    return _parseParameterGroup(params, rawValues, '');
+}