Add docs for OTLP Exponential Histogram (#5386)

docs/modules/ROOT/pages/implementations/otlp.adoc

@@ -70,7 +70,8 @@ https://opentelemetry.io/docs/specs/otel/metrics/data-model/#metric-points[Metri
 1. https://opentelemetry.io/docs/specs/otel/metrics/data-model/#sums[Sums, window=_blank]
 2. https://opentelemetry.io/docs/specs/otel/metrics/data-model/#gauge[Gauge, window=_blank]
 3. https://opentelemetry.io/docs/specs/otel/metrics/data-model/#histogram[Histogram, window=_blank]
-4. https://opentelemetry.io/docs/specs/otel/metrics/data-model/#summary-legacy[Summary, window=_blank]
+4. https://opentelemetry.io/docs/specs/otel/metrics/data-model/#exponentialhistogram[Exponential Histogram, window=_blank]
+5. https://opentelemetry.io/docs/specs/otel/metrics/data-model/#summary-legacy[Summary, window=_blank]
 
 The following table maps OTLP data points and the Micrometer meters:
 
@@ -84,12 +85,13 @@ The following table maps OTLP data points and the Micrometer meters:
 |Gauge
 |Gauge, TimeGauge, MultiGauge
 
-|Histogram
+|Histogram/Exponential Histogram^*^
 |Timer, DistributionSummary, LongTaskTimer, FunctionTimer (only sum and count are set)
 
 |Summary
 |Timer, DistributionSummary, LongTaskTimer
 |===
+__* - Histogram or Exponential Histogram is determined based on the configuration of the `OtlpMeterRegistry`. See below section for more info.__
 
 *Note*:
 
@@ -107,16 +109,25 @@ Micrometer `Timer` and `DistributionSummary` support configuring xref:/concepts/
 | Summary
 
 | publishPercentileHistogram
-| Histogram
+| Histogram/Exponential Histogram ^*^
 
 | serviceLevelObjectives
 | Histogram
 
 | publishPercentiles and (publishPercentileHistogram/serviceLevelObjectives)
 | Histogram
 |===
+__* The configuration `histogramFlavor` determines whether the OTLP DataPoint is a Histogram/Exponential Histogram.__
+
+`OtlpMeterRegistry` supports 2 types of Histogram implementations (1.Explicit Bucket Histogram (or simply called Histogram), 2. Exponential Histogram) when `publishPercentileHistogram` is configured. The choice is chosen by setting `histogramFlavor` in `OtlpConfig` used by registry. When the implementation is exponential histogram, it also supports 2 additional properties
+
+1. maxScale used to cap the maximum https://opentelemetry.io/docs/specs/otel/metrics/data-model/#exponential-scale[scale, window=_blank] used by the Exponential Histogram (defaults to 20).
+2. maxBuckets determines the maximum number of https://opentelemetry.io/docs/specs/otel/metrics/data-model/#exponential-buckets[buckets, window=_blank] to be used for exponential histograms (defaults to 160).
+
+Since Exponential Histogram cannot have custom SLO's specified, explicit bucket histogram is used whenever `serviceLevelObjectives` are added.
 
-Alternatively, if you use Spring Boot, you can use the https://docs.spring.io/spring-boot/docs/current/reference/htmlsingle/#actuator.metrics.customizing.per-meter-properties[per-meter properties, window=_blank] to configure this behavior.
+===  Configuration with Spring Boot
+If you use Spring Boot, you can use the https://docs.spring.io/spring-boot/docs/current/reference/htmlsingle/#actuator.metrics.customizing.per-meter-properties[per-meter properties, window=_blank] to configure this behavior.
 
 If you want to generate a Histogram data point for a Timer with name `test.timer` and default buckets generated by Micrometer, use: