feat: Add new Prometheus target and metadata API endpoints

[RiviaAzusa]

Add four new methods to PrometheusConnect class:

• get_scrape_pools(): Retrieve list of unique scrape pool names
• get_targets(): Get active/dropped targets with optional state and pool filters
• get_target_metadata(): Fetch metadata about metrics from specific targets
• get_metric_metadata(): Get metadata about metrics with optional filtering

These additions provide better visibility into Prometheus targets and metric
metadata, enabling more detailed monitoring and configuration analysis.

[4n4nd]

@RiviaAzusa this looks great but could you please add tests for these new functions?

[RiviaAzusa]

I have submitted the test cases, please review them and point out any errors if there are any.

[4n4nd]

Run PROM_URL="https://demo.promlabs.com/" pytest
============================= test session starts ==============================
platform linux -- Python 3.13.3, pytest-8.3.5, pluggy-1.5.0
rootdir: /home/runner/work/prometheus-api-client-python/prometheus-api-client-python
configfile: pyproject.toml
collected 48 items

tests/test_metric.py ..........                                          [ 20%]
tests/test_metric_range_df.py ........                                   [ 37%]
tests/test_metric_snapshot_df.py .......                                 [ 52%]
tests/test_metrics_list.py ....                                          [ 60%]
tests/test_prometheus_connect.py ...F....F..........                     [100%]

=================================== FAILURES ===================================
________________ TestPrometheusConnect.test_get_metric_metadata ________________

self = <tests.test_prometheus_connect.TestPrometheusConnect testMethod=test_get_metric_metadata>

    def test_get_metric_metadata(self):  # noqa D102
        metadata = self.pc.get_metric_metadata(metric=None)
        self.assertIsInstance(metadata, list)
        self.assertTrue(len(metadata) > 0, "no metric metadata found")
    
        # Check structure of metadata
        self.assertIn('metric_name', metadata[0])
        self.assertIn('type', metadata[0])
        self.assertIn('help', metadata[0])
        self.assertIn('unit', metadata[0])
    
        # Test with specific metric
        if len(metadata) > 0:
            metric_name = metadata[0]['metric_name']
            filtered_metadata = self.pc.get_metric_metadata(metric=metric_name)
            self.assertIsInstance(filtered_metadata, list)
            self.assertTrue(all(item['metric_name'] == metric_name for item in filtered_metadata))
    
        # Test with limit
>       limited_metadata = self.pc.get_metric_metadata(limit=1)
E       TypeError: PrometheusConnect.get_metric_metadata() missing 1 required positional argument: 'metric'

tests/test_prometheus_connect.py:205: TypeError
________________ TestPrometheusConnect.test_get_target_metadata ________________

self = <tests.test_prometheus_connect.TestPrometheusConnect testMethod=test_get_target_metadata>

    def test_get_target_metadata(self):  # noqa D102
        # Get a target to test with
        targets = self.pc.get_targets()
        if len(targets['activeTargets']) > 0:
            target = {
                'job': targets['activeTargets'][0]['labels']['job']
            }
            metadata = self.pc.get_target_metadata(target)
            self.assertIsInstance(metadata, list)
    
            # Test with metric filter
            if len(metadata) > 0:
                metric_name = metadata[0]['metric']
                filtered_metadata = self.pc.get_target_metadata(target, metric=metric_name)
                self.assertIsInstance(filtered_metadata, list)
>               self.assertTrue(all(item['metric'] == metric_name for item in filtered_metadata))

tests/test_prometheus_connect.py:180: 
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 

.0 = <list_iterator object at 0x7fbbdfdd3790>

>   self.assertTrue(all(item['metric'] == metric_name for item in filtered_metadata))
E   KeyError: 'metric'

tests/test_prometheus_connect.py:180: KeyError
=========================== short test summary info ============================
FAILED tests/test_prometheus_connect.py::TestPrometheusConnect::test_get_metric_metadata - TypeError: PrometheusConnect.get_metric_metadata() missing 1 required positional argument: 'metric'
FAILED tests/test_prometheus_connect.py::TestPrometheusConnect::test_get_target_metadata - KeyError: 'metric'
========================= 2 failed, 46 passed in 9.26s =========================
Error: Process completed with exit code 1.
0s
0s

[RiviaAzusa]

I have fixed the related bugs, please review again.

[4n4nd]

Thank you @RiviaAzusa!

[RiviaAzusa]

You are welcome @4n4nd !