Add expected Base64UrlEncoder.Decode overload for NET6 and 8

[pmaytak]

Fixes #3251

• Adds an overload for internal static int Decode(ReadOnlySpan<char> strSpan, Span<byte> output) with int return type for NET 6 and NET 8.
• Adds API tests.

Version	TFM	Method return value	Uses new Base64 API
<= 8.3.0	All	void	No
8.3.1 - 8.9.0	All	int	Yes
8.10.0 - 8.11.0	NET9	int	Yes
	ELSE	void	No
>= 8.12.0	NET9	int	Yes
	NET6, 8	int	No
	ELSE	void	No

Working notes which can be disregarded (just didn't want to lose them):

<= 8.3.0
internal static void Decode(ReadOnlySpan strSpan, Span output)

NET6+
private static int Decode(ReadOnlySpan strSpan, Span output, bool needReplace, int decodedLength)
ELSE
private static void Decode(ReadOnlySpan strSpan, Span output, bool needReplace, int decodedLength)

8.3.1 - 8.9.0
internal static int Decode(ReadOnlySpan strSpan, Span output)

NETCOREAPP
private static int Decode(ReadOnlySpan strSpan, Span output, int decodedLength)
ELSE
private static int Decode(ReadOnlySpan strSpan, Span output, int decodedLength)

8.10.0 - 8.11.0
NET9
int Decode(ReadOnlySpan strSpan, Span output)
ELSE
void Decode(ReadOnlySpan strSpan, Span output)

NET9
private static int Decode(ReadOnlySpan strSpan, Span output, int decodedLength)
NET6, NET8
private static int Decode(ReadOnlySpan strSpan, Span output, bool needReplace, int decodedLength)
ELSE
private static void Decode(ReadOnlySpan strSpan, Span output, bool needReplace, int decodedLength)

[github-actions]

Summary

Summary

Generated on:	5/30/2025 - 8:24:39 AM
Coverage date:	5/30/2025 - 8:14:28 AM - 5/30/2025 - 8:24:10 AM
Parser:	MultiReport (60x Cobertura)
Assemblies:	1
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Files:	2
Line coverage:	80.3% (620 of 772)
Covered lines:	620
Uncovered lines:	152
Coverable lines:	772
Total lines:	483
Branch coverage:	67.8% (228 of 336)
Covered branches:	228
Total branches:	336
Method coverage:	Feature is only available for sponsors

Coverage

Microsoft.IdentityModel.JsonWebTokens - 80.3%

Name	Line	Branch
Microsoft.IdentityModel.JsonWebTokens	80.3%	67.8%
Microsoft.IdentityModel.JsonWebTokens.JwtTokenUtilities	100%
System.Text.RegularExpressions.Generated	80.3%	67.8%
System.Text.RegularExpressions.Generated	80.3%	67.8%
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[mdchennu]

I'm really sorry about missing the different in returns for the Decode method, Peter. Thank you for noticing and fixing it. The change makes sense to me! I noticed a unit test (unrelated) was failing, so re-ran the job.

[github-actions]

Summary

Summary

Generated on:	5/30/2025 - 4:23:37 PM
Coverage date:	5/30/2025 - 4:13:21 PM - 5/30/2025 - 4:23:00 PM
Parser:	MultiReport (60x Cobertura)
Assemblies:	1
Classes:	7
Files:	2
Line coverage:	80.3% (620 of 772)
Covered lines:	620
Uncovered lines:	152
Coverable lines:	772
Total lines:	483
Branch coverage:	67.8% (228 of 336)
Covered branches:	228
Total branches:	336
Method coverage:	Feature is only available for sponsors

Coverage

Microsoft.IdentityModel.JsonWebTokens - 80.3%

Name	Line	Branch
Microsoft.IdentityModel.JsonWebTokens	80.3%	67.8%
Microsoft.IdentityModel.JsonWebTokens.JwtTokenUtilities	100%
System.Text.RegularExpressions.Generated	80.3%	67.8%
System.Text.RegularExpressions.Generated	80.3%	67.8%
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[keegan-caruso]

I would think we need to adjust the API files for this

[keegan-caruso]

It can be a follow up

[github-actions]

Summary

Summary

Generated on:	5/30/2025 - 8:34:41 PM
Coverage date:	5/30/2025 - 8:23:47 PM - 5/30/2025 - 8:34:11 PM
Parser:	MultiReport (60x Cobertura)
Assemblies:	1
Classes:	7
Files:	2
Line coverage:	80.3% (620 of 772)
Covered lines:	620
Uncovered lines:	152
Coverable lines:	772
Total lines:	483
Branch coverage:	67.8% (228 of 336)
Covered branches:	228
Total branches:	336
Method coverage:	Feature is only available for sponsors

Coverage

Microsoft.IdentityModel.JsonWebTokens - 80.3%

Name	Line	Branch
Microsoft.IdentityModel.JsonWebTokens	80.3%	67.8%
Microsoft.IdentityModel.JsonWebTokens.JwtTokenUtilities	100%
System.Text.RegularExpressions.Generated	80.3%	67.8%
System.Text.RegularExpressions.Generated	80.3%	67.8%
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