APIScan remediation: remove obsolete SharedTokenCacheUsername, fix masked CS0618 pragma, migrate obsolete ManagedIdentityCredential ctor - #4421

…e obsolete ManagedIdentityCredential ctor (#4421)

Cherry-pick of #4421 into release/6.1 (6.1.7). On this branch the provider
lives in the Microsoft.Data.SqlClient project rather than the
Microsoft.Data.SqlClient.Extensions.Azure project.

- Remove the obsolete DefaultAzureCredentialOptions.SharedTokenCacheUsername
  assignment (and its now-unneeded CS0618 pragma wrapper).
- Migrate the obsolete ManagedIdentityCredential(string, TokenCredentialOptions)
  constructor to ManagedIdentityCredential(ManagedIdentityCredentialOptions).

The masked-CS0618-pragma fix from #4421 does not apply here: the pragma is
already balanced (restore) on this branch.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Remove entries with no customer-visible effect, and reframe entries that
led with implementation detail rather than customer impact.

Removed:
- #3862 ConnectionCapabilities consolidation - internal refactor; the
  GetSchema("DataTypes") fix it enables is deferred to a later PR.
- #3700/#3741 SSRP scaffolding - adds no parsing code and no behavior change.
- #4517 CodeQL findings - PKCS#1 half is suppression comments for declared
  false positives; the SHA-1 removal is a no-op in practice.
- #4421 Extensions.Azure APIScan remediation - no public API change and
  managed-identity behavior preserved exactly; the removed assignment was
  already a no-op. Extensions.Azure now has no Changed section.

Promoted:
- #4504 counter fixes moved from a pool V2 sub-bullet into Fixed. These
  affect the default pool that customers use without opting in, and the
  previous text understated them as two fixes limited to Count.

Reframed:
- Cross-platform build collapsed to the one customer-visible outcome
  (trimming on Linux/macOS); package contents were always unchanged.
- #4528 now leads with the allocation regression rather than call-site count.
- AKV cache fixes now lead with symptoms (unbounded signature cache growth,
  duplicate CryptographyClient per key) rather than GetOrCreate/GetOrAdd.

Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>
Copilot-Session: 8c691319-4c66-40f6-a88e-b453937052f1

* Add release notes for 7.1.0-preview3

Adds release notes for Microsoft.Data.SqlClient 7.1.0-preview3 and its
four aligned companion packages, updates the per-version README index
tables, and adds the corresponding CHANGELOG entry.

Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>
Copilot-Session: c7425f3e-f6b8-439b-b74f-e25f8406fbf6

* Capture remaining closed 7.1.0-preview3 milestone items in release notes

Adds coverage for milestone items that closed after the initial draft:

- #4529 leaked-connection reclamation in ChannelDbConnectionPool
- #4535 SqlBulkCopy graph column alias mapping bypass
- #4521 / #4496 Entra ID tenant parsing for multi-segment STSURL authorities
- #4540 async key store provider APIs in the AzureKeyVaultProvider

Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>
Copilot-Session: c485150e-f46e-4c55-8d06-e0491a10e7e8

* Add #4439 and #4445 to 7.1.0-preview3 release notes

Both are user-facing fixes merged into the preview3 milestone that were
not yet captured in the release notes or CHANGELOG:

- #4439: DateOnly values in sql_variant TVP columns were sent as datetime
  instead of date, overflowing for values outside the datetime range.
- #4445: ServerCertificate pin validation was skipped when the platform
  reported no TLS policy errors, and an unloadable certificate file fell
  back to host-name validation instead of failing closed.

Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>
Copilot-Session: 8c691319-4c66-40f6-a88e-b453937052f1

* Add #4474 to 7.1.0-preview3 cross-platform build notes

PR #4474 (Remove OS-Specific Builds) removed OS-specific build targets
and output paths, and rewrote the MDS nuspec to source a single
OS-agnostic assembly for both the win and unix runtime folders.

Verified the nuspec change is src-path-only: all 52 file entries have
identical target= values before and after, so the produced package
layout is unchanged.

Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>
Copilot-Session: 8c691319-4c66-40f6-a88e-b453937052f1

* Clarify #4536 allocation fix applies to the default async read path

Addresses review feedback on PR #4565: the PacketData node-reuse fix is
not gated behind UseCompatibilityAsyncBehaviour or any other AppContext
switch, and the perf validation was measured on the default path.

Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>
Copilot-Session: 8c691319-4c66-40f6-a88e-b453937052f1

* Scope preview3 release notes to customer-facing changes

Remove entries with no customer-visible effect, and reframe entries that
led with implementation detail rather than customer impact.

Removed:
- #3862 ConnectionCapabilities consolidation - internal refactor; the
  GetSchema("DataTypes") fix it enables is deferred to a later PR.
- #3700/#3741 SSRP scaffolding - adds no parsing code and no behavior change.
- #4517 CodeQL findings - PKCS#1 half is suppression comments for declared
  false positives; the SHA-1 removal is a no-op in practice.
- #4421 Extensions.Azure APIScan remediation - no public API change and
  managed-identity behavior preserved exactly; the removed assignment was
  already a no-op. Extensions.Azure now has no Changed section.

Promoted:
- #4504 counter fixes moved from a pool V2 sub-bullet into Fixed. These
  affect the default pool that customers use without opting in, and the
  previous text understated them as two fixes limited to Count.

Reframed:
- Cross-platform build collapsed to the one customer-visible outcome
  (trimming on Linux/macOS); package contents were always unchanged.
- #4528 now leads with the allocation regression rather than call-site count.
- AKV cache fixes now lead with symptoms (unbounded signature cache growth,
  duplicate CryptographyClient per key) rather than GetOrCreate/GetOrAdd.

Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>
Copilot-Session: 8c691319-4c66-40f6-a88e-b453937052f1

---------

Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>
Copilot-Session: c7425f3e-f6b8-439b-b74f-e25f8406fbf6
Copilot-Session: c485150e-f46e-4c55-8d06-e0491a10e7e8
Copilot-Session: 8c691319-4c66-40f6-a88e-b453937052f1