Support http proxy servers when exchanging authcode for token

[cfryanr]

From a Slack conversation with Enrique Medina Montenegro.

Good morning from the Netherlands 🙂 Here is the info about the proxy issue:

My company uses a corporative proxy --> http://proxy.internal.mycompany.org:8080 <-- to provide access to the Internet

• If any Pod running in our K8s cluster needs outbound Internet access, then it must configure this proxy as env variables --> HTTP_PROXY, HTTPS_PROXY and NO_PROXY
• When using the auth-service, the first redirection to our Azure AD IdP is actually performed by the browser, so there is no issue here
• However, when the auth-service needs to exchange the authorization code for the access token, then it cannot due to not being able to access the Internet

Taking a look at the code, I see that you use the Boost.Beast library for HTTP matters, which claims not to have in its scope the addition of such proxy support:
https://groups.google.com/d/msg/boost-developers-archive/-Zf7f-dfcmA/BUAjLnngBAAJ

However, it seems to be pretty easy:
https://stackoverflow.com/questions/11523829/how-to-add-proxy-support-to-boostasio/11537603#11537603

These are the precise logs:

# kubectl logs productpage-v1-5c6798d7d4-mzhs9 -c authservice
[2019-12-03 08:04:48.487] [console] [info] RunServer: Server listening on 127.0.0.1:10003
[2019-12-03 08:05:01.305] [console] [trace] Check
[2019-12-03 08:05:01.305] [console] [trace] Matches
[2019-12-03 08:05:01.305] [console] [debug] Check: processing request ://bookinfo.dev.epocloud.altia.es/productpage with filter chain idp_filter_chain
[2019-12-03 08:05:01.305] [console] [trace] New
[2019-12-03 08:05:01.306] [console] [trace] OidcFilter
[2019-12-03 08:05:01.306] [console] [trace] Process
[2019-12-03 08:05:01.306] [console] [debug] Call from @172.16.20.105 to @172.16.135.3
[2019-12-03 08:05:01.306] [console] [info] GetTokenFromCookie: __Host-bookinfo-authservice-id-token-cookie token cookie missing
[2019-12-03 08:05:01.306] [console] [info] GetTokenFromCookie: __Host-bookinfo-authservice-access-token-cookie token cookie missing
[2019-12-03 08:05:01.306] [console] [trace] Process: checking handler for ://bookinfo.dev.epocloud.altia.es-/productpage
[2019-12-03 08:05:01.794] [console] [trace] Check
[2019-12-03 08:05:01.794] [console] [trace] Matches
[2019-12-03 08:05:01.794] [console] [debug] Check: processing request ://bookinfo.dev.epocloud.altia.es/productpage/oauth/callback?code=OAQABAAIAAACQN9QBRU3jT6bcBQLZNUj7FraunBPo2Anx9gyAxLsdu-bjmfQnfzP9GJZCGakYWsHRzeV_eP89xj8IlweogBgNVF-IJW88VHMjUF2mb1qBgxYUOcOhN4X0RovpJOv25ad5dUCGWpoHmK0n1Q04dDi5dYtbZDAYqPyc_xJmr-rwtSneZoVu7jL16aJ-cF6M96iJQSoZw5fUXlJDaECEls1FKHr6XOhsqtQYgyu8hEL9yt5r3ONyG7Oo6QDWheJi96axsOrOa4toF62bElJeVm4Rsv5C2FFEvMkTQJXXj1hEhc-zk-owBC4D8m5NVGKzRhwphgpkYtRBMyEZtouiJQReKRcGry4KbbXA87LDfM0S5XGX-Kyad7WHV3-s62gFwjW7QqyG0OUq2D6Obm0xIlnmlk6alUOowSAijHHbgf_zXlI34ACRW4pv7SqZ0b6SHtMEioJe0CNFCDBlUVC7Md3_9lCMoonwNoVpEHNE-9eOLKamC-sJyevrATPt6A-WX9HsWcPk3OBwiqnzwMP9DJxj7MLl6KATfLI0mmeswhluYLINKKuvhr6a6oWncaVK9HlsBjH-MYXoRv5kqoaMCh3tU6lNhFMHhUodCcwvPUG4CBDoPQ9UubmEctTyGway7viwDniuqfzP1hj1pVTH09ZrUcVgeSv4sEHeXgupQ4_j7lYtBqWaohHsoQngxVq5HvmSBA8qd_8_Qlxx3vXyGfXuZSFWaZghaKYKrRP7Dm8Dc9R8PvoliTBvL1fLh2KiyePncMfAalIh96NdN27zCLDtbLoNeJpf0NVvp-HXsBckBMxCxLsxMKm22UNLhB3wdSnBEND-HUFxCiPA1IzXsgCGoZW9cFvMFJtbIjyy3ZXkE7DJSewKjW4I7MIVABBEeccgAA&state=0w05_ITARWBE0BfMcW2oSNwFTMtiPRW3Iq_VBkLbAJY&session_state=c302d6d2-c392-424d-97d3-2579814617c4 with filter chain idp_filter_chain
[2019-12-03 08:05:01.794] [console] [trace] New
[2019-12-03 08:05:01.794] [console] [trace] OidcFilter
[2019-12-03 08:05:01.794] [console] [trace] Process
[2019-12-03 08:05:01.794] [console] [debug] Call from @172.16.20.105 to @172.16.135.3
[2019-12-03 08:05:01.795] [console] [info] GetTokenFromCookie: __Host-bookinfo-authservice-id-token-cookie token cookie missing
[2019-12-03 08:05:01.795] [console] [info] GetTokenFromCookie: __Host-bookinfo-authservice-access-token-cookie token cookie missing
[2019-12-03 08:05:01.795] [console] [trace] Process: checking handler for ://bookinfo.dev.epocloud.altia.es-/productpage/oauth/callback?code=OAQABAAIAAACQN9QBRU3jT6bcBQLZNUj7FraunBPo2Anx9gyAxLsdu-bjmfQnfzP9GJZCGakYWsHRzeV_eP89xj8IlweogBgNVF-IJW88VHMjUF2mb1qBgxYUOcOhN4X0RovpJOv25ad5dUCGWpoHmK0n1Q04dDi5dYtbZDAYqPyc_xJmr-rwtSneZoVu7jL16aJ-cF6M96iJQSoZw5fUXlJDaECEls1FKHr6XOhsqtQYgyu8hEL9yt5r3ONyG7Oo6QDWheJi96axsOrOa4toF62bElJeVm4Rsv5C2FFEvMkTQJXXj1hEhc-zk-owBC4D8m5NVGKzRhwphgpkYtRBMyEZtouiJQReKRcGry4KbbXA87LDfM0S5XGX-Kyad7WHV3-s62gFwjW7QqyG0OUq2D6Obm0xIlnmlk6alUOowSAijHHbgf_zXlI34ACRW4pv7SqZ0b6SHtMEioJe0CNFCDBlUVC7Md3_9lCMoonwNoVpEHNE-9eOLKamC-sJyevrATPt6A-WX9HsWcPk3OBwiqnzwMP9DJxj7MLl6KATfLI0mmeswhluYLINKKuvhr6a6oWncaVK9HlsBjH-MYXoRv5kqoaMCh3tU6lNhFMHhUodCcwvPUG4CBDoPQ9UubmEctTyGway7viwDniuqfzP1hj1pVTH09ZrUcVgeSv4sEHeXgupQ4_j7lYtBqWaohHsoQngxVq5HvmSBA8qd_8_Qlxx3vXyGfXuZSFWaZghaKYKrRP7Dm8Dc9R8PvoliTBvL1fLh2KiyePncMfAalIh96NdN27zCLDtbLoNeJpf0NVvp-HXsBckBMxCxLsxMKm22UNLhB3wdSnBEND-HUFxCiPA1IzXsgCGoZW9cFvMFJtbIjyy3ZXkE7DJSewKjW4I7MIVABBEeccgAA&state=0w05_ITARWBE0BfMcW2oSNwFTMtiPRW3Iq_VBkLbAJY&session_state=c302d6d2-c392-424d-97d3-2579814617c4
[2019-12-03 08:05:01.795] [console] [trace] RetrieveToken
[2019-12-03 08:05:01.795] [console] [trace] Post
[2019-12-03 08:05:01.860] [console] [info] Post: unexpected exception: handshake: WRONG_VERSION_NUMBER
[2019-12-03 08:05:01.860] [console] [info] RetrieveToken: HTTP error encountered: IdP connection error