Add TLS compatibility mode configuration for HTTP senders

[adhamahmad]

Summary

Adds support for configuring TLS compatibility mode for HTTP senders (OkHttp only for now), allowing clients to optionally connect to endpoints that require legacy TLS protocol versions.

Fixes #7573

Motivation

Some users running on legacy environments, may be unable to connect to endpoints that only support older TLS protocol versions. The current HTTP sender configuration only supports modern TLS negotiation, preventing connections to these legacy endpoints.

Changes

Added TlsCompatibilityMode configuration to HttpSenderConfig with MODERN as the default behavior
Added HttpExporterBuilder.setTlsCompatibilityMode(TlsCompatibilityMode) to allow OTLP HTTP exporters to configure TLS compatibility behavior
Updated ImmutableHttpSenderConfig to carry the TLS compatibility mode configuration
Updated OkHttpHttpSender to map TlsCompatibilityMode.COMPATIBLE to OkHttp's ConnectionSpec.COMPATIBLE_TLS
Kept existing behavior unchanged by defaulting all senders to modern TLS configuration
Added TlsCompatibilityMode as a public API for implementation-neutral TLS compatibility configuration
Updated public API diff documentation with the new configuration method and enum

Testing

Added OkHttpHttpSenderTlsCompatibilityTest
Verified MODERN mode cannot connect to a server restricted to TLSv1/TLSv1.1 protocols
Verified COMPATIBLE mode can negotiate a connection with a legacy TLS-only server

[linux-foundation-easycla]

The committers listed above are authorized under a signed CLA.

• ✅ login: adhamahmad / name: Adham Ahmed Hussein Mahrous (6473f3a)

[otelbot]

⚠️ API changes detected — additional maintainer review required

@jack-berg @jkwatson

This PR modifies the public API surface area of the following module(s):

• opentelemetry-sdk-common

Please review the changes in docs/apidiffs/current_vs_latest/ carefully before approving.

[jack-berg]

Hey I gave this issue some thought and shared my analysis here: #7573 (comment)

I think we should go in a different direction with this: #8610, which embodies option d in the comment.

[opentelemetry-pr-dashboard]

Pull request dashboard status

Waiting on the author · refreshed 2026-07-29 18:23 UTC

Respond to 1 review item (e.g. link a commit, explain why not, ask a follow-up):

• Top-level threads: 1

Status above doesn't look right?

• Just replied or pushed? Anything around or after the refresh time above may not be picked up yet — give it a few minutes.
• Should this be with reviewers? Comment /dashboard route:reviewers to route it to them.
• Anything wrong — including the routing? Report it with what you expected; it helps us improve the dashboard.

[opentelemetry-pr-dashboard]

Hi @adhamahmad — just a friendly reminder that this pull request has been waiting on you for a week.

There are still items that need your attention. See the dashboard status comment for the full list. You don't need to push a code change to hand it back — replying to move each discussion forward is enough, whether that's answering a question, explaining why no change is needed, or asking a follow-up. The dashboard then automatically routes it back to reviewers.

If you believe this pull request is incorrectly routed as waiting on the author, comment /dashboard route:reviewers to route it from waiting on the author to waiting on reviewers.