Fix : invalid params when using ignore trailing slash

[tigerwill90]

Description

This PR fixes an issue related to the new "ignore trailing slash" feature. Unlike the "redirect trailing slash" option, when "ignore trailing slash" is enabled, the correct route handler is expected to be called with the appropriate parameters for the matched route. However, this wasn't always the case due to the evaluation of different paths with wildcard segments.

Problem

Given the following routes:

• /api/{a}
• /api/foo/{b}

When a request is made to /api/foo/bar/ with "ignore trailing slash" enabled, the expected match is /api/foo/{b}, but the parameters were not always correctly assigned. The evaluation process was as follows (also see priority rules):

1. /api/foo/{b}: Records "bar" as the parameter for {b}, and marks it for a trailing slash recommendation (tsr).
2. /api/{a}: Matches /api/foo, drops {b} parameter, and records "foo" as the parameter for {a}.
3. Since no previous match, falls back to the first tsr, /api/foo/{b}, and calls the handler.

During step 2, the parameters recorded in step 1 were lost, resulting in the correct handler being called but with incorrect parameters.

Solution

The fix ensures that parameters are preserved when encountering the first trailing slash recommendation (tsr). This way, when falling back to the initially matched route, the correct parameters are retained and passed to the handler.

Benchmark Differential

Expect no impact on performance (small optimisation have been achieved on the lookup function.).

goos: linux
goarch: amd64
pkg: github.com/tigerwill90/fox
cpu: Intel(R) Core(TM) i9-9900K CPU @ 3.60GHz
                    │   old.txt   │              new.txt               │
                    │   sec/op    │   sec/op     vs base               │
StaticAll-16          11.36µ ± 2%   11.01µ ± 1%  -3.01% (p=0.000 n=10)
GithubParamsAll-16    84.29n ± 1%   82.11n ± 1%  -2.58% (p=0.000 n=10)
OverlappingRoute-16   96.45n ± 1%   98.48n ± 2%  +2.10% (p=0.007 n=10)
StaticParallel-16     9.398n ± 4%   9.521n ± 1%       ~ (p=0.239 n=10)
CatchAll-16           34.06n ± 6%   31.56n ± 2%  -7.34% (p=0.000 n=10)
CatchAllParallel-16   5.732n ± 7%   5.803n ± 6%       ~ (p=0.529 n=10)
CloneWith-16          65.94n ± 1%   66.19n ± 2%       ~ (p=0.684 n=10)
geomean               73.11n        72.25n       -1.18%

[codecov]

Codecov Report

Attention: Patch coverage is 83.87097% with 10 lines in your changes missing coverage. Please review.

Project coverage is 87.15%. Comparing base (74b75c6) to head (5a8c0e4).

Files	Patch %	Lines
tree.go	84.00%	4 Missing and 4 partials ⚠️
context.go	60.00%	1 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master      #34      +/-   ##
==========================================
- Coverage   87.38%   87.15%   -0.24%     
==========================================
  Files          15       15              
  Lines        1911     1939      +28     
==========================================
+ Hits         1670     1690      +20     
- Misses        189      193       +4     
- Partials       52       56       +4     

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