feat: Identity API response caching

[einsteinx2]

Summary

• Adds caching of identify and login calls
• Clears that cache on modify and logout calls
• Some minor code cleanup

This is all behind a feature flag that is currently disabled

Testing Plan

• Unit tests were added
• Tested locally:

1. Disable feature flag

mParticle -> Identity response code: 200
mParticle -> Identity execution time: 437.32ms
mParticle -> Identity response:
{"context":null,"matched_identities":{"email":"bbaron+abc1@mparticle.com"},"is_ephemeral":false,"mpid":"6167123318226482339","is_logged_in":true}

2. Start app fresh (idenity should save to cache)

mParticle -> Identity Caching - max age header value (in seconds): 86400
mParticle -> Identity Caching - Cached response for endpoint 2, key: 2::8f9e2eefac54a94a33bcfa00512550bf4963e21ee01060a924fc181bd55981a0, expires: 2024-01-10 21:51:30 +0000, bodyData.length: 145

3. Start app again (identity should read from cache)

mParticle -> Identity Caching - Valid cached response found for key: 2::8f9e2eefac54a94a33bcfa00512550bf4963e21ee01060a924fc181bd55981a0, expires: 2024-01-10 21:51:30 +0000, seconds left: 86357.1
mParticle -> Identity execution time: 0.36ms
mParticle -> Identity response:
{"context":null,"matched_identities":{"email":"bbaron+abc1@mparticle.com"},"is_ephemeral":false,"mpid":"6167123318226482339","is_logged_in":true}

4. Manually call identify, then modify, then identify (should save identify, should clear cache on modify, should save identify)

// First identify request
mParticle -> Identity response code: 200
mParticle -> Identity Caching - max age header value (in seconds): 86400
mParticle -> Identity Caching - Cached response for endpoint 2, key: 2::b6fb24420bffaaeded2d230e03aa287d82dbb13a9b5a04832992fa49ca605361, expires: 2024-01-10 21:55:53 +0000, bodyData.length: 145
mParticle -> Identity execution time: 235.59ms

// Modify request
mParticle -> Identity Caching - Removed all cached responses
mParticle -> Identity response code: 200
mParticle -> Identity Caching - max age header value (in seconds): 86400
mParticle -> Identity execution time: 372.21ms

// Second identify request
mParticle -> Identity response code: 200
mParticle -> Identity Caching - max age header value (in seconds): 86400
mParticle -> Identity Caching - Cached response for endpoint 2, key: 2::b6fb24420bffaaeded2d230e03aa287d82dbb13a9b5a04832992fa49ca605361, expires: 2024-01-10 21:55:54 +0000, bodyData.length: 145
mParticle -> Identity execution time: 252.73ms

Reference Issue (For mParticle employees only. Ignore if you are an outside contributor)

• Closes https://go.mparticle.com/work/SQDSDKS-5974

[mparticle-automation]

:tada: This PR is included in version 8.18.0 :tada:

The release is available on GitHub release

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