Add HTTP-agnostic protocol, shared exceptions, and mock fixtures to base

[mwdd146980]

What does this PR do?

Lands the backend-neutral HTTP foundation on master, decoupled from the feature branch, so integrations and tests can build against an HTTP-agnostic surface. It adds:

• HTTP-agnostic protocol types: HTTPClientProtocol and HTTPResponseProtocol (http_protocol.py).
• A shared, backend-neutral exception hierarchy (http_exceptions.py).
• A MockHTTPResponse test double (http_testing.py) plus new mock_http, mock_openmetrics_http, and mock_prometheus_http dev fixtures.
• New capabilities on RequestsWrapper: trust_env, close, get_cookie, get_header, set_header.
• A create_http_client factory seam on AgentCheck so the backing HTTP client is overridable.

The change is purely additive. self.http still raises requests exceptions, the existing mock_response fixtures are unchanged, and no integration catch sites are touched, so there is no behavior change.

Motivation

We want to migrate the shipped Agent off requests behind an HTTP-agnostic surface. This PR moves the non-breaking foundation (proto, shared exception types, mock fixtures, wrapper capabilities, and the factory seam) to master first, so we can adopt the surface incrementally.

Verification

• http.py diff vs master is additive only: 46 insertions, 0 removals, and zero references to the exception-translation machinery (_translate_*, http_exceptions, requests_exceptions). The verbs, raise_for_status, and ResponseWrapper are byte-identical to master, so self.http behavior is unchanged.
• Base HTTP test suite: 170 passed, including the new test_capabilities.py and test_http_testing.py, the appended get_header/set_header tests, and the create_http_client factory tests. The remaining errors/failures are pre-existing environmental gaps (jwt, requests_kerberos, socks proxy) that fail identically on master.
• Lint and formatting pass through ddev test --lint datadog_checks_base datadog_checks_dev (ruff format and ruff check: all checks passed).

Review checklist (to be filled by reviewers)

• Feature or bugfix MUST have appropriate tests (unit, integration, e2e)
• Add qa/required if this PR needs QA validation, or qa/skip-qa if it does not. Exactly one of the two is required. (qa/skip-qa: additive surface, no shipped check uses it yet, self.http behavior unchanged.)
• If you need to backport this PR to another branch, you can add the backport/<branch-name> label to the PR and it will automatically open a backport PR once this one is merged

[dd-octo-sts]

Validation Report

All 21 validations passed.

Show details

Validation	Description	Status
agent-reqs	Verify check versions match the Agent requirements file	✅
ci	Validate CI configuration and code coverage settings	✅
codeowners	Validate every integration has a CODEOWNERS entry	✅
config	Validate default configuration files against spec.yaml	✅
dep	Verify dependency pins are consistent and Agent-compatible	✅
http	Validate integrations use the HTTP wrapper correctly	✅
imports	Validate check imports do not use deprecated modules	✅
integration-style	Validate check code style conventions	✅
jmx-metrics	Validate JMX metrics definition files and config	✅
labeler	Validate PR labeler config matches integration directories	✅
legacy-signature	Validate no integration uses the legacy Agent check signature	✅
license-headers	Validate Python files have proper license headers	✅
licenses	Validate third-party license attribution list	✅
metadata	Validate metadata.csv metric definitions	✅
models	Validate configuration data models match spec.yaml	✅
openmetrics	Validate OpenMetrics integrations disable the metric limit	✅
package	Validate Python package metadata and naming	✅
qa-label	Validate the pull request declares whether it needs QA for the next Agent release	✅
readmes	Validate README files have required sections	✅
saved-views	Validate saved view JSON file structure and fields	✅
version	Validate version consistency between package and changelog	✅

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[datadog-datadog-prod-us1-2]

   

✨ Fix all issues with BitsAI

⚠️ Warnings

🚦 3 Pipeline jobs failed

PR All | test / j06ca546 / SNMP     

PR All | test / j44368ad (py3.13-17.0-C) / Postgres-py3.13-17.0-C     

PR All | test / jaee58c5 / Kong     

🧪 2 Tests failed in 1 job

PR All | run  

test_e2e_discovery_all_candidates from test_integration_e2e.py  

Container logs matched 'error' after probing candidate #1: 'error'

❄️ Known flaky: test_e2e_snmp_listener from test_e2e_snmp_listener.py  

Needed at least 1 candidates for 'datadog.snmp.check_duration', got 0
Expected:
        MetricStub(name='datadog.snmp.check_duration', type=0, value=None, tags=['autodiscovery_subnet:172.18.0.0/28', 'device_vendor:apc', 'firmware_version:2.0.3-test', 'loader:python', 'model:APC Smart-UPS 600', 'serial_num:test_serial', 'snmp_device:172.18.0.1', 'snmp_profile:apc_ups', 'ups_name:testIdentName'], hostname=None, device=None, flush_first_value=None)
Difference to closest:
        Expected tag snmp_device:172.18.0.1
        Found snmp_device:172.18.0.2

Similar submitted:
Score   Most similar
1.00    MetricStub(name='datadog.snmp.check_duration', type=0, value=0.13117408752441406, tags=['autodiscovery_subnet:172.18.0.0/28', 'device_vendor:apc', 'firmware_version:2.0.3-test', 'loader:python', 'model:APC Smart-UPS 600', 'serial_num:test_serial', 'snmp_device:172.18.0.2', 'snmp_profile:apc_ups', 'ups_name:testIdentName'], hostname='runnervmos4r4', device=None, flush_first_value=False)
...

Not introduced in this PR.

ℹ️ Info

No other issues found (see more)

❄️ No new flaky tests detected

🎯 Code Coverage (details)
• Patch Coverage: 90.17%
• Overall Coverage: 88.38% (+0.10%)

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