improv: update metrics interface to resemble other core utils

[to-mc]

Issue #, if available:#33

Description of changes:

Update Metrics to accept a "service" parameter to match Logger/Tracer. This parameter will be used as the metric namespace. Deprecated MetricManager.add_namespace env var.

BREAKING: Remove POWERTOOLS_METRICS_NAMESPACE, in favour of using the same environment variable as Logger/Tracer classes (POWERTOOLS_SERVICE_NAME).

• Meet tenets criteria
• Update tests
• Update docs
• PR title follows conventional commit semantics

[codecov-commenter]

Codecov Report

Merging #60 into develop will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@ Coverage Diff @@## develop #60 +/- ##
========================================
Coverage 99.38% 99.39% ========================================
Files 15 15 Lines 489 492 +3 Branches 44 44 ========================================
+ Hits 486 489 +3 
Misses 3 3 

Impacted Files	Coverage Δ
aws_lambda_powertools/metrics/base.py	100.00% <100.00%> (ø)
aws_lambda_powertools/metrics/metric.py	100.00% <100.00%> (ø)
aws_lambda_powertools/metrics/metrics.py	100.00% <100.00%> (ø)

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[heitorlessa]

LGTM - Minor typo only

[heitorlessa]

Are you still planning to add the service as a dimension? or will that be in a separate PR?

Could you also change docstring in line 89 in metrics.py:

 **Lambda function using tracer and metrics decorators**
metrics = Metrics()

Thanks again, Tom!!

[to-mc]

Are you still planning to add the service as a dimension? or will that be in a separate PR?

I'm in two minds about adding a dimension with the service name. I'll create a separate issue/PR for that to discuss.

Could you also change docstring in line 89 in metrics.py:

 **Lambda function using tracer and metrics decorators**
metrics = Metrics()

Done!

Thanks again, Tom!!

[heitorlessa]

LGTM!