fix: api errors related to postage stamps

[aloknerurkar]

This PR attempts to solve #2026 in part.

This particular change tries to address the postage bucket full error which is annoying as the user does not understand that he cannot use the batch anymore.

We can create a separate errors.go file in pkg/api which could house all these error case handlers. This way we can edit the same file from time to time to add special case handling.

@acud @agazso @AuHau @Eknir

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This change is 

[agazso]

Sending PSS message with the postage bucket full may lead to similar issue (see #1988).

@aloknerurkar do you plan to address that in this PR as well?

[zelig]

Reviewed 4 of 4 files at r1, 1 of 1 files at r2.
Reviewable status: complete! all files reviewed, all discussions resolved (waiting on @acud, @AuHau, and @Eknir)

[mrekucci]

Since the jsonhttp.PaymentRequired returns 402, all the affected endpoint definitions in openapi/Swarm.yaml should be also adjusted accordingly.

Reviewable status: complete! all files reviewed, all discussions resolved (waiting on @acud, @AuHau, and @Eknir)

[acud]

Reviewed 1 of 4 files at r1.
Reviewable status: all files reviewed, 1 unresolved discussion (waiting on @aloknerurkar, @AuHau, and @Eknir)

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pkg/api/bzz.go, line 36 at r2 (raw file):

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func mappedHTTPErr(w http.ResponseWriter, e error, defaultMsg interface{}) {

i think that having such a pattern would be useful if all middlewares would just return an error to an upper layer middleware that would then translate the actual errors into a response. but since we don't do this I would vote for explicitly handling the errors within the handlers

[aloknerurkar]

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pkg/api/bzz.go, line 36 at r2 (raw file):

Previously, acud (acud) wrote…

i think that having such a pattern would be useful if all middlewares would just return an error to an upper layer middleware that would then translate the actual errors into a response. but since we don't do this I would vote for explicitly handling the errors within the handlers

Done.

[aloknerurkar]

Dismissed @acud from a discussion.
Reviewable status: 0 of 7 files reviewed, all discussions resolved (waiting on @acud, @AuHau, @Eknir, and @zelig)

[acud]

Reviewed 7 of 7 files at r3.
Reviewable status: complete! all files reviewed, all discussions resolved (waiting on @AuHau, @Eknir, and @mrekucci)

[acud]

Reviewable status: complete! all files reviewed, all discussions resolved (waiting on @AuHau, @Eknir, and @mrekucci)

[mrekucci]

Reviewed 7 of 7 files at r3.
Reviewable status: complete! all files reviewed, all discussions resolved (waiting on @AuHau and @Eknir)