Feature/real time flags (#5)

[gazreese]

Description

This PR adds the real time flags feature as described in #18 and Flagsmith/flagsmith#1498

Fixes #18

Type of change

Please delete options that are not relevant.

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

How Has This Been Tested?

Because the real-time updates are dependent upon the the operation of the SSE functionality I found it best to write end-to-end integrations test for this feature. They test the main 'update' scenario, as well as ensuring that the SSE connection reconnects. It

Test Configuration:

As these are integration tests they need some environment variables to connect to an account, feature and value. These are at the top of the integration test and follow the format seen in the existing documentation:

    // You'll need a valid account to test this
    private val environmentKey = System.getenv("ENV_KEY")
    private val authToken = "Token " + System.getenv("API_TOKEN")
    private val featureId = System.getenv("FEATURE_ID") ?: "integration-test-feature"
    private val featureStateId = System.getenv("FEATURE_STATE_ID") ?: "313512"

To skip the integration tests you can run the gradle command as shown in the build.gradle:

    // if the excludeIntegrationTests property is set
    // then exclude tests with IntegrationTest in the name
    // i.e. `gradle :FlagsmithClient:testDebugUnitTest --tests "com.flagsmith.*" -P excludeIntegrationTests`
    if (project.hasProperty("excludeIntegrationTests")) {
        exclude {
            it.name.contains("IntegrationTest")
        }
    }

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my code
• The code is peer-reviewed
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published in downstream modules

Changes

• Compiles and test, need to add some tests then get it into a sample app

• Should be testing but not getting the errors through Fuse so can't run into the logic

• Probably gone as far as I can with 2.x fuel, let's try the 3.x

• Move to Retrofit - seems to be going well so far, test runs

• Tidying up, setTrait test not working

• All the tests are passing so will finish the retrofit migration

• Updated some of the logic and added setTraits

• Checkpoint commit before trying generic converter

• Generics working fine

• All passing for flags and such with the new generic caching

• Mostly swapped to Retrofit, now need to do the analytics

• Analytics now over to retrofit

• Add caching for the getFlags endpoint

• Get rid of the last of Fuel

• Another clear-out and all working fine on the tests

• Now using Retrofit cache, remove the old stuff

• Now just using HTTP caching

• Delete the old caching logic

• Finishing off, should be done for defaults and caching

• Remove unneeded todo

• Remove some more code

• Still just playing around with it

• Move cache configuration to its own data class

• Tidy up the cache config and the tests

• Update the comments

• Now covers the caching tests

• Tidy up some more of the tests

• Some more tidying up

• Default to caching disabled

• Last few PR comments

• Split the read and write timeout for HTTP

• Initial basic implementation, let's try to get things hooked up to the server

• Seems to be generally working

• Checkpoint commit, seems to be generally working now just need to get the flags on update

• Checkpoint commit before making the changes OK'd by Matthew to move the update clock into the event service

• Ensure that the event source just reconnects if it loses the connection

• Events and timers now all hooked-up and working in the manual integration test

• Got the integration test working

• Tidy everything up and move sensitive data to environment variables

• Add a new test to cover the event stream going through a reconnect cycle

• Added test for the live stream of flags, tidied up the imports and various thing, changed the logic a bit for when we need to do updates from events