Only generate headers once in EventService

This patchset builds on
https://gerrit.openbmc-project.xyz/c/openbmc/bmcweb/+/45761 and moves
the header generation into the constructor, rather than attempting to
repurpose addHeaders().

Tested:
Per Appu:
"Did basic check and its initialized to default as before."

Per Sunitha:
"Tested the basic event notification scenario with this commit. Works
fine"

https://gerrit.openbmc-project.xyz/c/openbmc/bmcweb/+/46703/2

Signed-off-by: Ed Tanous <edtanous@google.com>
Change-Id: Ia9e8b89574c7e0137f0d93f08378e45c2fcf5376
diff --git a/http/http_client.hpp b/http/http_client.hpp
index 53040ae..cd67398 100644
--- a/http/http_client.hpp
+++ b/http/http_client.hpp
@@ -134,15 +134,6 @@
     {
         state = ConnState::sendInProgress;
 
-        BMCWEB_LOG_DEBUG << __FUNCTION__ << "(): " << host << ":" << port;
-
-        req.version(static_cast<int>(11)); // HTTP 1.1
-        req.target(uri);
-        req.method(boost::beast::http::verb::post);
-
-        req.set(boost::beast::http::field::host, host);
-        req.keep_alive(true);
-
         req.body() = data;
         req.prepare_payload();
 
@@ -390,13 +381,17 @@
   public:
     explicit HttpClient(boost::asio::io_context& ioc, const std::string& id,
                         const std::string& destIP, const std::string& destPort,
-                        const std::string& destUri) :
+                        const std::string& destUri,
+                        const boost::beast::http::fields& httpHeader) :
         conn(ioc),
-        timer(ioc), subId(id), host(destIP), port(destPort), uri(destUri),
-        retryCount(0), maxRetryAttempts(5), retryIntervalSecs(0),
+        timer(ioc),
+        req(boost::beast::http::verb::post, destUri, 11, "", httpHeader),
+        state(ConnState::initialized), subId(id), host(destIP), port(destPort),
+        uri(destUri), retryCount(0), maxRetryAttempts(5), retryIntervalSecs(0),
         retryPolicyAction("TerminateAfterRetries"), runningTimer(false)
     {
-        state = ConnState::initialized;
+        req.set(boost::beast::http::field::host, host);
+        req.keep_alive(true);
     }
 
     void sendData(const std::string& data)
@@ -419,11 +414,6 @@
         return;
     }
 
-    void setHeaders(const boost::beast::http::fields& httpHeaders)
-    {
-        req.base() = boost::beast::http::header<true>(httpHeaders);
-    }
-
     void setRetryConfig(const uint32_t retryAttempts,
                         const uint32_t retryTimeoutInterval)
     {