Rewrite HTTP GET polling task to use mbedtls library

The http_get task has been rewritten to use mbedtls instead of BearSSL.
I'm seeing better luck with this library's success rate, although it
still fails on x508 certificate verification intermittently.

Makefile

@@ -10,8 +10,7 @@ ESPTOOL_ARGS+=-fs 4MB
 EXTRA_CFLAGS+=-I./lib/esp-gdbstub/include
 EXTRA_LDFLAGS+=-L./lib/esp-gdbstub/lib
 
-EXTRA_COMPONENTS = extras/bearssl
-EXTRA_CFLAGS +=-DCONFIG_EPOCH_TIME=$(shell date --utc '+%s')
+EXTRA_COMPONENTS = extras/mbedtls
 
 include ./lib/esp-open-rtos/common.mk
 

src/cert.c

@@ -0,0 +1,44 @@
+/* This is the CA certificate for the CA trust chain of
+   www.howsmyssl.com in PEM format, as dumped via:
+
+   openssl s_client -showcerts -connect www.howsmyssl.com:443 </dev/null
+
+   The CA cert is the last cert in the chain output by the server.
+*/
+#include <stdio.h>
+#include <stdint.h>
+#include <string.h>
+
+/*
+ * 1 s:C = BE, O = GlobalSign nv-sa, CN = GlobalSign CloudSSL CA - SHA256 - G3
+ * i:C = BE, O = GlobalSign nv-sa, OU = Root CA, CN = GlobalSign Root CA
+ */
+const char *server_root_cert = "-----BEGIN CERTIFICATE-----\r\n"
+"MIIEizCCA3OgAwIBAgIORvCM288sVGbvMwHdXzQwDQYJKoZIhvcNAQELBQAwVzEL\r\n"
+"MAkGA1UEBhMCQkUxGTAXBgNVBAoTEEdsb2JhbFNpZ24gbnYtc2ExEDAOBgNVBAsT\r\n"
+"B1Jvb3QgQ0ExGzAZBgNVBAMTEkdsb2JhbFNpZ24gUm9vdCBDQTAeFw0xNTA4MTkw\r\n"
+"MDAwMDBaFw0yNTA4MTkwMDAwMDBaMFcxCzAJBgNVBAYTAkJFMRkwFwYDVQQKExBH\r\n"
+"bG9iYWxTaWduIG52LXNhMS0wKwYDVQQDEyRHbG9iYWxTaWduIENsb3VkU1NMIENB\r\n"
+"IC0gU0hBMjU2IC0gRzMwggEiMA0GCSqGSIb3DQEBAQUAA4IBDwAwggEKAoIBAQCj\r\n"
+"wHXhMpjl2a6EfI3oI19GlVtMoiVw15AEhYDJtfSKZU2Sy6XEQqC2eSUx7fGFIM0T\r\n"
+"UT1nrJdNaJszhlyzey2q33egYdH1PPua/NPVlMrJHoAbkJDIrI32YBecMbjFYaLi\r\n"
+"blclCG8kmZnPlL/Hi2uwH8oU+hibbBB8mSvaSmPlsk7C/T4QC0j0dwsv8JZLOu69\r\n"
+"Nd6FjdoTDs4BxHHT03fFCKZgOSWnJ2lcg9FvdnjuxURbRb0pO+LGCQ+ivivc41za\r\n"
+"Wm+O58kHa36hwFOVgongeFxyqGy+Z2ur5zPZh/L4XCf09io7h+/awkfav6zrJ2R7\r\n"
+"TFPrNOEvmyBNVBJrfSi9AgMBAAGjggFTMIIBTzAOBgNVHQ8BAf8EBAMCAQYwHQYD\r\n"
+"VR0lBBYwFAYIKwYBBQUHAwEGCCsGAQUFBwMCMBIGA1UdEwEB/wQIMAYBAf8CAQAw\r\n"
+"HQYDVR0OBBYEFKkrh+HOJEc7G7/PhTcCVZ0NlFjmMB8GA1UdIwQYMBaAFGB7ZhpF\r\n"
+"DZfKiVAvfQTNNKj//P1LMD0GCCsGAQUFBwEBBDEwLzAtBggrBgEFBQcwAYYhaHR0\r\n"
+"cDovL29jc3AuZ2xvYmFsc2lnbi5jb20vcm9vdHIxMDMGA1UdHwQsMCowKKAmoCSG\r\n"
+"Imh0dHA6Ly9jcmwuZ2xvYmFsc2lnbi5jb20vcm9vdC5jcmwwVgYDVR0gBE8wTTAL\r\n"
+"BgkrBgEEAaAyARQwPgYGZ4EMAQICMDQwMgYIKwYBBQUHAgEWJmh0dHBzOi8vd3d3\r\n"
+"Lmdsb2JhbHNpZ24uY29tL3JlcG9zaXRvcnkvMA0GCSqGSIb3DQEBCwUAA4IBAQCi\r\n"
+"HWmKCo7EFIMqKhJNOSeQTvCNrNKWYkc2XpLR+sWTtTcHZSnS9FNQa8n0/jT13bgd\r\n"
+"+vzcFKxWlCecQqoETbftWNmZ0knmIC/Tp3e4Koka76fPhi3WU+kLk5xOq9lF7qSE\r\n"
+"hf805A7Au6XOX5WJhXCqwV3szyvT2YPfA8qBpwIyt3dhECVO2XTz2XmCtSZwtFK8\r\n"
+"jzPXiq4Z0PySrS+6PKBIWEde/SBWlSDBch2rZpmk1Xg3SBufskw3Z3r9QtLTVp7T\r\n"
+"HY7EDGiWtkdREPd76xUJZPX58GMWLT3fI0I6k2PMq69PVwbH/hRVYs4nERnh9ELt\r\n"
+"IjBrNRpKBYCkZd/My2/Q\r\n"
+"-----END CERTIFICATE-----\r\n";
+
+