Add a helper filter to collect requets processing metrics

[codecov[bot]]

Codecov Report

Base: 89.42% // Head: 89.41% // Decreases project coverage by -0.01% :warning:

Coverage data is based on head (1693757) compared to base (29ca831). Patch coverage: 94.28% of modified lines in pull request are covered.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #39 +/- ## ============================================ - Coverage 89.42% 89.41% -0.01% - Complexity 1924 1929 +5 ============================================ Files 138 139 +1 Lines 4472 4507 +35 Branches 619 625 +6 ============================================ + Hits 3999 4030 +31 - Misses 327 329 +2 - Partials 146 148 +2 ``` | [Impacted Files](https://codecov.io/gh/open-coap/java-coap/pull/39?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=open-coap) | Coverage Δ | | |---|---|---| | [...ap/metrics/micrometer/MicrometerMetricsFilter.java](https://codecov.io/gh/open-coap/java-coap/pull/39?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=open-coap#diff-Y29hcC1tZXRyaWNzL3NyYy9tYWluL2phdmEvb3JnL29wZW5jb2FwL2NvYXAvbWV0cmljcy9taWNyb21ldGVyL01pY3JvbWV0ZXJNZXRyaWNzRmlsdGVyLmphdmE=) | `94.28% <94.28%> (ø)` | | | [.../coap/transport/javassl/SocketClientTransport.java](https://codecov.io/gh/open-coap/java-coap/pull/39?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=open-coap#diff-Y29hcC10Y3Avc3JjL21haW4vamF2YS9jb20vbWJlZC9jb2FwL3RyYW5zcG9ydC9qYXZhc3NsL1NvY2tldENsaWVudFRyYW5zcG9ydC5qYXZh) | `71.64% <0.00%> (-2.99%)` | :arrow_down: | Help us with your feedback. Take ten seconds to tell us [how you rate us](https://about.codecov.io/nps?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=open-coap). Have a feature suggestion? [Share it here.](https://app.codecov.io/gh/feedback/?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=open-coap)

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