fix: ensure all http headers get lower cased (#7823)

Author: bojbrook

packages/datadog-plugin-http/src/client.js

@@ -211,7 +211,7 @@ function getHeaders (config) {
     if (typeof header === 'string') {
       const separatorIndex = header.indexOf(':')
       result.push(separatorIndex === -1
-        ? [header, undefined]
+        ? [header.toLowerCase(), undefined]
         : [
             header.slice(0, separatorIndex).toLowerCase(),
             header.slice(separatorIndex + 1),

packages/datadog-plugin-http/test/client.spec.js

@@ -1185,7 +1185,7 @@ describe('Plugin', () => {
           config = {
             server: false,
             client: {
-              headers: ['host', 'x-foo', 'x-bar:http.bar', 'x-baz:http.baz'],
+              headers: ['host', 'x-foo', 'x-bar:http.bar', 'x-baz:http.baz', 'X-Request-Id'],
             },
           }
 
@@ -1211,6 +1211,7 @@ describe('Plugin', () => {
                 const meta = traces[0][0].meta
 
                 assert.strictEqual(meta[`${HTTP_REQUEST_HEADERS}.host`], `localhost:${port}`)
+                assert.strictEqual(meta[`${HTTP_REQUEST_HEADERS}.x-request-id`], 'request-id')
                 assert.strictEqual(meta['http.baz'], 'baz')
                 assert.strictEqual(meta[`${HTTP_RESPONSE_HEADERS}.x-foo`], 'foo')
                 assert.strictEqual(meta['http.bar'], 'bar')
@@ -1219,7 +1220,7 @@ describe('Plugin', () => {
               .catch(done)
 
             const url = `${protocol}://localhost:${port}/user`
-            const headers = { 'x-baz': 'baz' }
+            const headers = { 'x-baz': 'baz', 'X-Request-Id': 'request-id' }
             const req = http.request(url, { headers }, res => {
               res.on('data', () => {})
             })