Add support for fine-grained websocket filtering

[aaslamin]

Issue: aporeto-inc/aporeto#1699

ℹ️ This PR is building on-top of API changes to elemental introduced here: aporeto-inc/elemental#61

---

This PR:

• ⚠️ Breaking change: add new method to the Session interface, PushConfig, to make it possible to retrieve the push config currently active on the session.

Note: this was done so that this callback:

1. has enough context to decide whether it is worth parsing the entire identifiable
2. be able to do fine-grain identity filtering via https://github.com/aporeto-inc/elemental/blob/master/matcher.go#L10

• 🔥 Remove usage of deprecated type elemental.PushFilter; replaced with the re-named equivalent elemental.PushConfig

• Parse the identity filters upon receipt of a elemental.PushConfig to avoid having to parse them on each push event received by the push server

  • in the event that parsing fails, the socket is closed.

TODO:

• test for new session method
• test for verifying parsing logic on receipt of an elemental.PushConfig from connected client
  • happy path
  • error case where the parsing fails - socket should get closed

[aaslamin]

/build - automatically fired by gogo with following PRs and commit SHAs v1.0.0

[
  {
    "project": "websocket-filtering",
    "component": "elemental",
    "pr-id": "61",
    "commit-sha": "fe1cdd68fa5787ec71e7a33771ecd34bcefe2c7d"
  },
  {
    "project": "websocket-filtering",
    "component": "bahamut",
    "pr-id": "82",
    "commit-sha": "8973cff17ff60c1940fa600393b557811878b43a"
  }
]

[t00f]

/build - automatically fired by gogo with following PRs and commit SHAs v1.0.0

[
  {
    "project": "websocket-filtering",
    "component": "bahamut",
    "pr-id": "82",
    "commit-sha": "8973cff17ff60c1940fa600393b557811878b43a"
  },
  {
    "project": "websocket-filtering",
    "component": "elemental",
    "pr-id": "61",
    "commit-sha": "fe1cdd68fa5787ec71e7a33771ecd34bcefe2c7d"
  }
]

[aaslamin]

Update

• Added ability for the 'ShouldDispatch' callee to close the socket based on the error type it returns.

If ShouldDispatch returns an error type that has the method ShouldCloseSocket() (bool, int) then it can inform whether the socket should be closed along with a code to use in the close message. This is useful in cases where it makes no sense to continue serving the client (e.g. the client configured a semantically invalid push config, for example: they used a comparator that is not yet supported/implemented).

FYI: @primalmotion

[aaslamin]

/build - automatically fired by gogo with following PRs and commit SHAs v1.0.0

[
  {
    "project": "websocket-filtering",
    "component": "elemental",
    "pr-id": "61",
    "commit-sha": "a1aa1431ac568f5a19c9793f9226696291b4a108"
  },
  {
    "project": "websocket-filtering",
    "component": "bahamut",
    "pr-id": "82",
    "commit-sha": "26fda9ee660a1039b385e811ff7cdf4b18b37d90"
  },
  {
    "project": "websocket-filtering",
    "component": "backend",
    "pr-id": "639",
    "commit-sha": "7a8e3502b96300b6f3d982622fa49b102b3e8c99"
  }
]

[aaslamin]

/build - automatically fired by gogo with following PRs and commit SHAs v1.0.0

[
  {
    "project": "websocket-filtering",
    "component": "elemental",
    "pr-id": "61",
    "commit-sha": "8f033610ca1b9e881c44f6420f3d7a45a74d2a86"
  },
  {
    "project": "websocket-filtering",
    "component": "bahamut",
    "pr-id": "82",
    "commit-sha": "26fda9ee660a1039b385e811ff7cdf4b18b37d90"
  },
  {
    "project": "websocket-filtering",
    "component": "backend",
    "pr-id": "639",
    "commit-sha": "7a8e3502b96300b6f3d982622fa49b102b3e8c99"
  }
]

[aaslamin]

/build - automatically fired by gogo with following PRs and commit SHAs v1.0.0

[
  {
    "project": "websocket-filtering",
    "component": "elemental",
    "pr-id": "61",
    "commit-sha": "8f033610ca1b9e881c44f6420f3d7a45a74d2a86"
  },
  {
    "project": "websocket-filtering",
    "component": "bahamut",
    "pr-id": "82",
    "commit-sha": "26fda9ee660a1039b385e811ff7cdf4b18b37d90"
  },
  {
    "project": "websocket-filtering",
    "component": "backend",
    "pr-id": "639",
    "commit-sha": "2499382adb60ae51cbf64ee78e9c9caf1e961519"
  }
]