fix: lowercase boolean URL params (local=true, deleteAll=true)

NGSI-LD § 4 (URL parameter conventions) and RFC 3986 § 6.2.2.1 both specify that URL parameter values are case-sensitive. The spec uses the literal lowercase tokens true and false throughout.

Nine call sites across eight tests passed local=${True} (or ${true}) — Robot Framework's ${True}/${true} is Python's True, which the requests library serializes as the string "True" (capital T) in URL parameters. Plus one deleteAll=${true} in 046_22_08. Brokers that strictly enforce the spec's case-sensitive convention correctly reject this as 400 BadRequestData ("'local' must be 'true' or 'false' (lowercase); got 'True'"); the affected tests were never reaching their intended assertions.

This MR replaces all nine occurrences with the literal lowercase true.

Affected tests

File Param
046_22_08.robot deleteAll=true on DELETE attrs
D010_01_exc.robot local=true (setup Create Entity)
D010_02_exc.robot local=true (main retrieve + setup)
D010_02_red.robot local=true (main retrieve)
D002_01_exc.robot local=true (setup)
D002_02_exc.robot local=true (setup)
D003_02_exc.robot local=true (setup)
D004_01_exc.robot local=true (setup)

Verified on swBroker (a strict-case broker)

Test Before After
046_22_08 FAIL 400 PASS
D010_02_red FAIL 400 PASS
D010_02_exc FAIL PASS
D002_01_exc FAIL PASS
D010_01_exc FAIL FAIL '0 > 0' should be true (stub never called)
D002_02_exc FAIL FAIL Setup 201 != 409 (expects pre-existing entity)
D003_02_exc FAIL FAIL Timeout: request was not received
D004_01_exc FAIL FAIL 204 != 400 (broker accepts what test expected rejected)

The remaining four tests now fail at strictly later errors — none show the parseBool 400 anymore. They expose unrelated test-side or broker-logic issues that the case-sensitivity rejection had been masking; those will be addressed independently.

Spec angle

Per § 4: URL parameter values are case-sensitive. Brokers that accept True / TRUE are forgiving beyond what the spec mandates. The conformance test suite should send the spec form to test what the spec actually requires.

Documented as testsuite-doubts.md #81 (closed) (in a parallel MR queue).

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