chore: fix routes trailing slashes inconsistencies to avoid validation errors

[viniarck]

Closes #236

• I've also adapted some 4XX status code accordingly.

Local Tests

• Reran all test suites 4 times with this branch and all starlette PRs related that are in code review:

+ python3 -m pytest tests/ --reruns 2 -r fEr
============================= test session starts ==============================
platform linux -- Python 3.9.2, pytest-7.2.0, pluggy-1.0.0
rootdir: /builds/amlight/kytos-end-to-end-tester/kytos-end-to-end-tests
plugins: rerunfailures-10.2, timeout-2.1.0, anyio-3.6.2
collected 227 items
tests/test_e2e_01_kytos_startup.py ..                                    [  0%]
tests/test_e2e_05_topology.py ..................                         [  8%]
tests/test_e2e_10_mef_eline.py ..........ss.....x.....x................  [ 26%]
tests/test_e2e_11_mef_eline.py ......                                    [ 29%]
tests/test_e2e_12_mef_eline.py .....Xx.                                  [ 32%]
tests/test_e2e_13_mef_eline.py .....xs.s......xs.s.XXxX.xxxx..X......... [ 50%]
...                                                                      [ 51%]
tests/test_e2e_14_mef_eline.py x                                         [ 52%]
tests/test_e2e_15_mef_eline.py ..                                        [ 53%]
tests/test_e2e_20_flow_manager.py .....................                  [ 62%]
tests/test_e2e_21_flow_manager.py ...                                    [ 63%]
tests/test_e2e_22_flow_manager.py ...............                        [ 70%]
tests/test_e2e_23_flow_manager.py ..............                         [ 76%]
tests/test_e2e_30_of_lldp.py ....                                        [ 78%]
tests/test_e2e_31_of_lldp.py ...                                         [ 79%]
tests/test_e2e_32_of_lldp.py ...                                         [ 81%]
tests/test_e2e_40_sdntrace.py ...........                                [ 85%]
tests/test_e2e_41_kytos_auth.py ........                                 [ 89%]
tests/test_e2e_50_maintenance.py ........................                [100%]
=============================== warnings summary ===============================
= 205 passed, 6 skipped, 11 xfailed, 5 xpassed, 799 warnings in 10406.12s (2:53:26) =

Out of 4 executions, only a single rerun happened it was the same as this old one that had been reported on issue #234

[viniarck]

Related PRs have landed.